Hiya!
Yeah...I have always strongly disliked that particular element of the 1e DMG. For one, because it encourages another type of thinking that I think is poisonous to the game: classifying members of the hobby as "players" xor "DMs." If DMs are supposed to keep their players in the dark about the rules, then no DM should be willing to run a game for someone who has DM experience...which means becoming a DM is a one-way street, you can check out but you can never leave. Anything which discourages DMs from considering taking up the mantle is probably a bad idea, considering how dire the shortage of DMs, and particularly of good DMs, seems to be. And for two, the suggested ways to deal with people who do have and make use of "secret DM knowledge" were incredibly petty and mean-spirited. Essentially, it (or at least what I've heard of it) is "they're definitely obviously cheating, so feel free to punish/torture their characters as much as you like until they stop." But when "stop" means "stop having secret DM knowledge"...
But yeah, the 5e approach appears to be like how an actual student council works (rather than the absurd student council clubs of anime). It's the DM's world, you're just witnessing it. If she graciously deigns to let you choose/have/do something, that is her prerogative. If she does not, that, too, is her prerogative. If she selects a particular course of action or story which the players happen to find cool/exciting/interesting, it is not because they put it forward, but because she elected to choose it. If you dislike it, you can feel free to go to hell close the door on your way out; what is decided is decided, and woe betide the one who questions the viking hat.
(If my rhetoric doesn't make it clear: I'm really not a fan of this style. A refusal to compromise or adapt in a game--refusal to even believe that compromise/adaptation could ever be useful or necessary at the gaming table--is a pretty serious issue in my eyes.)
Short version:
Discouraging non-DM's from reading stuff not in the PHB was primarily for two things.
First, to distinctly differentiate the Players role from the DM's role. Just like the top dogs at WotC don't disseminate their confidential memos about where they want to take the D&D brand, to everyone that works for them. Same idea; those who are not "in control of the operation" don't
need to know any of that stuff, and by not knowing it, it differentiates the roles between Player and DM. That difference allows the DM leeway for the introduction of his/her own 'stuff' (rules, items, monsters, etc) and no Player would know the difference. Encountering a Ettercap for the first time, or a Vanderlaang for the first time....the Players would see both on "equal footing". This leads into...
Second, mystery. It allows "mystery" for the Players. The Players don't know the monsters. They don't know the magic items. They don't know their chances for surviving being thrown into a deep river, being swept down rapids, whilst wearing their backpack, weapons and armor. From their perspective they just use their
imaginations to picture the situation. From there, they role-play what their character would do to try and survive. Dread and excitement ensue! The DM tells them to make this roll, or that save, or some other check... and the Player rolls, not knowing the exact details. Excitement in the face of the unknown is a KEY (if not THE key) ingredient of playing an RPG in the first place. By keeping the players from "peeking behind the curtain" (as some wise writer once said), it helps maintain that mystery. As soon as you have a Player instantly flip open the PHB, then make some quick calculations, roll a d20, then blurt out,
"Ok. I made my Swim check with all the appropriate modifiers. I beat the DC for River - Rapids by 6... so I swim to shore"... well, you've just (A) erased that distinction between DM and Player, and (B) sucked
all the mystery and excitement out of would could have been a wonderfully dramatic situation.
So, while I understand your stance on it, I don't think you've thought through the actual consequences of what the 3e+ "Everyone can read every book" action. I
NEVER has as many arguments with players as I do when I'm trying to DM players who have grown up with 3.x/4e/PF. Virtually
every ruling or adjudication I make is questioned and dissected. Books are flipped open, rules are pointed out, Feats are read aloud, etc, etc, etc. I have to explain why their roll of 22 failed when the rules say the DC check is a 18 at maximum. If I don't, kittens are lost in epic fashion. Giving in, I finally say
"Guys! It's a fricken illusion! OK?! See!? THAT'S why you 'failed'...because the illusion makes you 'fail'." Aaaaaannnd.... POOF! Mystery gone. DM authority undermined. Future situations with
anything "not in the rules", negated. No thank you. I will not play/DM in that kind of game.
And, as a final note, you not liking the distinction between Player and DM is just something you'll have to live with. You can try and delude yourself into thinking both are "the same", but they aren't. And they
SHOULDN'T be. Not any more than the players in a sport should have equal say in rulings made by the referee. The Ref is there to maintain structure and fairness. This should lead to the players enjoying the game more. Yes, they may argue with this call or that, but ultimately they
know that the Ref is
not "just another player"... and that he/she is outside all that stuff. A Referee in an RPG is the very similar; he/she is
not a player. Different responsibilities and different goals. Why do people play sports? Because they enjoy it. Why do people Referee sports? Because they enjoy it. Claiming that both types (players and refs) should be treated "equal" is...silly, IMHO.
PS: As for "punishing DM's when they play", I don't think so. It advocates punishing those who abuse it; those who use their knowledge above and beyond what their PC's may reasonably know. That said...any DM worth his salt would have a LOT of different things anyway. So a DM playing in another's game may have his DM knowledge bite him in the butt by making the assumption that Rule X works as per the DMG Page XX; when in fact, in this DM's game, it has been modified significantly. This all ties back into the "Players don't need to know" thing quite nicely.
^_^
Paul L. Ming