Players can occasionally pull some silly stuff with tiny hut, but if you really want to see why the impenetrable forcefield version of the spell is bad game design, give it to an NPC defending a dungeon the PCs have to clear. Now you have a bunker filled with hallway after hallway of impenetrable forcefields that don't inconvenience any of the dungeon's defenders. And that's not some super-optimized, high-level strategy. That's just a mid-level mage saying, "Hey, I have this spell designed to protect us when we Long Rest, and this dungeon is where we take our Long Rests, so..."