Ever since D&D, many TTRPG's have had these two axes of character advancement- what you get from "experience" (be it levels or increasing individual traits) and what you get from "treasure".
Treasure has always been the province of the person running the game, and for many years, there was no real guidance on what players should/could have. It was scattershot, up to DM will or whatever was in the adventure.
This led to treasure tables that were random, but weighted to yield specific results, and modules stuffed with things everyone would want- I couldn't tell you how many +1 long swords or rings of protection players at my tables have earned over the years due to this.
Sometimes, however, a character concept requires a specific bit of treasure, and games have wrestled over the years on how to get the items into the hands of players. A Star Wars game might allow Jedi, but what is a Jedi without a lightsaber? Star Wars SAGA solves this by giving a Jedi a lightsaber as a class feature. But this then leads to the question of "how much is this feature worth" when balancing classes. And then, if later on, the players find a lightsaber, how much does this devalue the class feature?
Other games try to fix this by having magic items be purchased or crafted, but this leads to pushback from people who feel magic items should be exceptionally rare or "special", as opposed to just gear characters equip, which isn't helped by the scores of rather mundane items (the +1 long swords and rings of protection for example).
The random, scattershot approach also leads to wildly different play experiences- the guy who finds a +1 longsword at level 2 has a very different experience than the guy who finds one at level 7, and a suit of +2 armor found at low levels has a very different impact than one found at level 13!
WotC initially tried to balance this by assuming that players would get magic items, but this got a lot of pushback from the people who didn't want players festooned with magical swag, so nowadays, they passed the buck- if a DM gives a player access to a magic item, on their own head be it! And the same is also true if they don't give players magic items!
And now, a 3e story!
I had a new player come to me with this fantastic character idea they had, inspired by some show they were watching. In it, a character had a "laser whip", and they wanted to build a PC around using something similar.
Whips being very underused in most games, I was on board with the idea, but the issue of how to get the whip in the hands of the player was something I wrestled with. The cost of a +1 brilliant energy whip-dagger (can't be a normal whip, because the rules said they were useless against any creature with natural armor and I wasn't sure if brilliant energy would get around that) was prohibitive and not something they could get early. So I switched gears and decided on a +1 flaming whip-dagger.
I couldn't really let them start with it at level 1, so I seeded it in a level 3 adventure. The player struggled with their normal whip-dagger for a few levels, as it's damage was low, and they had yet to acquire the abilities to make it useful, thus most of the time they were forced to use a sword.
Then tragedy struck. The character actually died on the adventure the magic whip was in, and the player was no longer interested in a whip user, so made a new character. So that when the magic whip was found, it was now an oddity that nobody was built to get much use out of!*
*Though at least, being 3e, it could be sold for extra cash later.
To this day, a lot of cool magic items I put into my adventures don't get used, for various reasons. And a magic item nobody wants is not "special" in any shape or form, thus I have to give players some way to use it down the road, either to sell, trade, or use as a gift or bribe to some NPC.
A magic item can be the most amazing, wonderful thing, but if it doesn't do what the player needs it to do, it's meaningless. Which is why I feel that letting players have at least some agency with regards to treasure can be a good thing!
Another example- I have a dual wielding Fighter in my current game. He uses short swords. During an adventure, they were able to find a truly fantastic item, the wonder blade, a magical dagger requiring attunment that occasionally produces a random, miraculous event on a natural 20 or 1. I thought they would carry this item for a long time, but session after session, it never triggered, despite my having made a table of possible results for it to spice up the game!
Last session, they defeated an enemy swordsman, and recovered his weapon, silver flash, a +1 short sword that produces light like a bullseye lantern and does an additional d6 radiant damage to undead. "Hey, now this is what I'm talking about! That's useful! And no attunement? I don't need that dagger anymore!"
I felt that in my very soul, but it was a valuable lesson.