Hiya!
But this would be a complaint about referees; whereas the post I replied to seemed to be complaining about players.
Sorry if it came off that way...that wasn't what I was intending. I was just saying that when I was learning to play and DM, that we made stuff up every single time we played. New monsters, spells, items, rules, etc. We didn't turn to a supplement because, well, we didn't have any available to us. Hell, I remember my first encounter with Dragon magazine. I found it in a hobby shop in West Edmonton Mall when my family forced me to go with them (c'mon...I was
13 years old! I was totally grown up and all that...geez mom! 
). It was Dragon #83 iirc...maybe #81. Wow. STUFF! For AD&D!
When I saw what kind of stuff was in there, and what kind of stuff I had created...and realized that my stuff was at least as good/balanced as the pro's...well, my fate as a DM was sealed. I've been DM'ing primarily for about 36 years now, since I was 10.
There's also the issue of workload - if I want to play such-and-such a character, and someone else has already designed it (and perhaps even playtested it), why reinvent the wheel?
Mainly for the fun and satisfaction of it. Why do people paint pictures of fruit in a bowl if they can just go out and buy one? Because creating it makes it "yours", and with that comes an intimate appreciation for it and the knowledge that "next time I'll do better and not put as much blue in the grapes" (e.g., you will improve your DM/Playing capability as well as your creative process).
Plopping down $40, writing "
Uber-Swordmaster - Longsword" on your character sheet, and then letting the DM read the entry from Splat Book XYZ does
absolutely nothing to help you improve your game/capability/fun (imho, of course).
This doesn't seem correct to me. If the GM wants to have use of super-berries irritate local druids, s/he can have the published equivalent do the same.
If the GM is rewarding plauyer inventiveness/imagination by imposing a % chance to lower INT, I'm not sure the word "reward" is being appropriately used. (Depending on edition, I guess - in early D&D stat-raising items, fountains etc were pretty common but they're pretty rare in contempary D&D.)
And if you're worried about players "rules lawyering" published material, do you think they're going to cheerfully take % chances of stat loss?
As others have pointed out, it's the "DM created with player input" vs. "It says so right here in the rules" that makes the difference. And a large one at that.
A friend of mine, Chris, was the 'second DM' during my first 10 or so years of DM'ing. He would create stuff and I would steal it. I would create stuff, and he would steal it. There's an old artist saying that goes something like:
"Good artists copy. Great artists steal. -Pablo Picasso". Anyway, he had a reoccurring NPC called "Sillius Fatbelly". He was a planes-hopping merchant charlatan of all manner of wares. He would sell you a Longsword +3...but there was ALWAYS a catch. Maybe it caused everyone around you to suffer -1 to all rolls, or maybe it was uniquely designed and stolen...and the Death Knight who owned it wants it back, or maybe it was intelligent and prone to loud sobbing and complaining every time it killed something, etc.
You know what effect Sillius Fatbelly's "wares" had on our game? Some of the most memorable and amazing role-playing situations we had. Yes, even the player who spent ALL his gold and threw in all his magic items just to get that +3 sword. In terms of this thread, the player eating the super-berry and then rolling % each time, eventually failing, and loosing d3 points of Int wouldn't be "upset" (as in actually p'oed) about it. He'd be laughing right along with everyone else, and then he'd start planning how to get his lost INT points back, and then start using super-berries only when absolutely needed.
But...if these were simply in that $40 Splat Book XYZ, with no loss mentioned, and then the DM threw that at him? I'd bet dimes to dollars that most players nowadays wouldn't find it amusing. They'd cry foul, point at the books, and then say something like
"If I knew I could loose INT points, there's no way I would have used them!", and be
actually upset about the 'surprise'. Then he'd keep whining until the DM ret-conned the situation. Then the player would keep the super-berries he has. And then the player would use them quite happily
after he already found a means of skirting the rules somehow and avoiding INT loss (like some particular feat combo, or spell/race thing, or magic-item/spell shenanigans that says something that says 'any Int, Wis or Cha losses come first from these temporary Int/Wis/Cha gains'.
Anyway, this is starting to sound quite ranty...and I really don't want it to. It was just nice to be reminded that I'm not "doing it wrong" and that I'm not a "bad DM that can't handle actual rules supplements", or that I'm somehow "a lazy or bad DM because I can't handle player creativity" ('creativity' referring to rules mastery and optimization).
I'm so grateful that I grew up learning 'on my own'...and that doing all that DM-learning on my own, by making my own stuff up, and seeing it either fail or succeed to various degrees has, IMHO, made me a better DM.
When I read a complaint about players not being creative enough, because they want to use published material, I don't see a GM who wants to reward player engagement with the game. I see a GM who wants to exercise a high level of control over the game.
And saying to a player or GM "Just make it up" is not a helpful reply to a request for advice. Giving advice on how to make things up (eg what is an appropriate % chance for INT loss when eating a super-berry) is part-and-parcel of talking about the game. It's been going on since the first number of The Strategic Review, Alarums and Excursions, etc was published.
First, a DM who wants a high level of control over his game isn't a bad thing if it makes his game lasting and fun. In my experience a DM who doesn't much care about 'controlling' his/her game (e.g. "If you own the book you can use it", for example)...typically don't have lasting games. They may be fun...but only for a short period of time, maybe a half-dozen play sessions or so. Then it breaks down and just becomes silly/pointless and everyone looses interest. IME, anyway.
I also firmly believe that telling a newbie asking for DM advice to "Not worry about it and just make some stuff up!" is MUCH more helpful than giving him/her a bunch of standard, typical, reading lists to follow.
EXCEPTIONS: Articles that treat the DM as something more than "a player who rolls for the monsters". Articles that discuss the 'boring' stuff...economics, political structures, race relations, terrain effects on survivability, etc. All that stuff that has almost NOTHING to do with the Player Characters, at least not in a direct, "ability/feat/skill/etc" way. Articles about dungeon ecology, or aquatic considerations for adventuring, etc. THAT is all great stuff for a DM to read. If an aspiring DM poo-poos all that stuff and "juts wants to make exciting adventures for his players", that's fine...but said DM will never be a great DM, or really even a good one. Competent, sure, nothing wrong with just blowing off steam and playing D&D for the Sh's and Gig's. But to become a "real" DM (e.g., one that creates their own campaign world with it's own quirks, secrets, pitfalls, and believability)? Not gonna cut it. Such a DM needs to know about all that "boring stuff" and then apply it to their own creative muse in regard to their own campaign).
^_^
Paul L. Ming