I've fired a handgun in an enclosed area a few times without hearing protection. It is NO fun and I doubt the sanity of anyone that would do it on a regular basis.
As far as wearing hearing protection if something goes bump in the night, your hearing is a major self-defense tool, especially in a low light situation. I would not want to be wearing anything that compromised my ability to hear if I was in a self-defense situation where the threat hasn't yet been identified and dealt with. You may hear something that directs your attention in the right direction well before you see the threat. I say this recognizing that once the first shot is fired your ability to hear is going to be seriously diminished.