I very much get the impression that for many groups, this is basically what happens. The players don't even specifically search for the treasure. As soon as the foe is defeated, the DM provides them with an exact list of the treasure they find. I've even got into arguments at Enworld with DMs or players that insist that treasure should never be hidden, because if it is hidden, then it raises the risk that the players might not find it.
Yeah, my group never really bothered with searching for our treasure. For us, it's less entitelment, and more an issue of time/laziness. As a player, I donly get to play like 4-6 hours per week. I don't want to spend an hour each session scouring the dungeon for the treasure. In fact, I'd like all loot and buying issues to be done outside of game time, so there's more time to adventure. This is also why for my current online game, I like the current system. People just get what they need and document it in a forum, and game time is almost completely shopping-free.
As a DM, not only do I not want ot spend game time on the matter, I'm also lazy. If the players are finding the items piece by piece as they go alon, they'll rightfully expect to be able to use them later in the dungeon if they can identify the stuff properly (or possibly even if not

). Thus far, i have NEVER made out treasure found lists until after the dungeon. I just don't want to do it. I also might change things around mid-dungeon from the original plans if




happens, which could affect what they get. So working on a mutual agreement of putting out a list post-dungeon, assuming they search for it as they explore, just works for us.
I have played in games where this wasn't the case, and was fine with it. It is fun to find an item and use it in that same lair, if the DM knows beforehand what's in the dungeon to find. And it can even be fun, as a Rogue or similar class, knowing you got "extra" goodies because you thought to check that wall which was actually a secret door.
I might handle things more strictly in the future, but not for now. And I do at least set limits by gp (and sometimes "oddness") of an item on whether it can be found at X. FWIW, I'm in my twenties, and 95% of the people I've ever gamed with have been 25 or younger. And the other 5% were all online, with me never even seeing said person face to face. I've seen some of the sense of entitlement you talk about (and have it myself), but not to such a horrible extent. I don't think any particular item should be "off limits" forever, if it's allowed in the campaign and is appropriate for the level of the character. If it's something rare, turn it into a quest, after the PC researches it. But I'm not into the whole adversarial, "You want this item? Well, now that you told me, you're not going to get it..." view.