I think most players are gonna at least check all the boxes to make sure they don't miss anything important, because if you're experienced with CRPGs
They could make them account-wide. If you dont get all from your first play-through, get them from second one. I generally hate design what forces player to do something, like in DOS2, there was billion places to loot and check.
I like the idea of replaying the game. Sure theres enough depth/stuff to play it again. Play the game, take what you want, if it feels you wanna go for another play-through, you get the rest. Thats why I would sell another Character Pack, btw. They could add somekind of vision-mode, for all lootables. Or Detect Item spell?
Account-wide? I don't understand what you mean. The implication of what you're saying is-I think-that at some point after you've replayed the game enough, you'll run out of loot and there won't be any in the containers anymore, which seems like a bad idea. Even assuming someone only ever plays two playthroughs, what if they just loot everything or basically everything in their first playthrough and then are left with basically nothing after that for their second? And what's a Character Pack? Is it literally a pack that characters carry, or is it something that directly effects the play of the game?
I mean, you need food for resting, and that right there is a reason to constantly be checking boxes.
Dunno ... i had so many Supply Bags so i didnt even used them all, therefore i also never needed even single piece of regular food.

But yeah, i get the urge to at least look everywhere ...
I have this condition asweel, but i also dont mind doing that at all.

I mean this is what we asked for isnt it? :P
We wanted immersion ... there is immersion, enjoy.

I approached the game by getting as much singular pieces of food as possible because I didn't want tospend money on supply packs unless I really couldn't avoid it, since I wanted to have money saved for weapons and potions and stuff. Somehow i'm always hard-up for gold in my playthroughs, or at least it feels that way. Furthermore, I've been trained by games to be paranoid and to think that any container could contain something that might be useful or interesting somewhere down the line. Frankly BG3 feels like exactly the sort of game where finding an innocuous item turns out to impact something later down the road, so that's all the more reason for me to continually rummage. I would not put it past them to plant some "old stick" somewhere and then reveal later if we picked it up that it's actually some kind of wand or artifact. There's nothing like that in the game now, but we only know that because we've played through this section over and over again. On a first-time playthrough, you have no idea what to expect.
I think MrToucan really hits the nail on the head when he asks what purpose the containers serve. Does having all these containers actually make the game more fun? If a feature in the game world is more likely to detract from the fun of playng the game and ignoring that feature is the reccomended way to enjoy the game, then that feature's inclusion is a detriment, and the game continues to be enjoyable in spite of its presence rather than because of it.