I think the camping supply "feature" is just annoying. Because you can go to the next inn buy the stuff and go back to the dungeon. So it's just a waste of time and not really a way to make it more "realistic" or "roleplayable" or whatever. I guess it's meant to be a middle ground of "not allowed to rest here" and "rest whenever you want". But as I said: it's basically just timewaisting.
Only thing is maybe, that it makes you calculate a bit: How many fights can i do (or how big is the dungeon) before i run out of supplies, because it's too annoying to leave the dungeon(dungeonpart) unfinished before going back.