You can stalk up on healing potions all you want, they won't get spell slots back. I am not advocating for long resting after each fight, but neither do I want to spend my real time navigating out of the dungeon just so I can run back again to fight.
Sure, now it leads to strange interactions like long resting while being inside a castle full of enemies. But say we implement the "no rest inside dungeon" approach - I would sneak my way out (which face it, players will outwit the AI any day), long rest, return. That is about 10 min irl time wasted on something that is not fun to do.
