I think the reason some (not all) of the issue your raise comes up is because there is no general agreement, in RPGing. on the extent to which the fictional world, beyond immediate details like the dungeon walls and traps, should matter to play. Are they part of the focus of play, or a mere backdrop to establish some degree of verisimilitude (like the role of the completely abstract "home base" suggested by Moldvay in his Basic set)?Unique (AFAICT) to ttrpgs though, a large number of people for a variety of reasons will bend over backwards in an attempt to make all roleplaying "equal" in quality. So, no matter what a character does; actions that conflict with stated motives or previous charachterization, anachronisms, using knowlege the character couldn't have, exploiting fringe-case rules, it's all perfect roleplaying and no more "realistic" than a player that tries to consider all the factors and act in the way that character would actually act in that situation. I understand some of the motivations for why people think this way, though I obviously don't agree. I think we would be much better off admitting when some people do a good job at something, like we do in all other walks of life.
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I have seen players sleeping out in the woods and players buying every luxury in town, both can make sense from an in character perspective and it's usually pretty clear when that's the case vs when the players are making the choice by largely ignoring the fictional world.
If you're playing that latter sort of game, then expecting players to have their PCs care about bathing as something they would pay for with their hard-won treasure seems ike a category error.
Where I think some confusion arises is when someone is running the second sort of game but think s they're running the first sort. I've seen this happen more than once in real life, and have read accounts of it also.