Why Carry A Holstered Gun At Home?
The same reason you wear a seat belt in your car, buy life insurance, health insurance, etc....
You don't get in your car thinking 'I'm going to go get into an automobile collision, so I better wear my seat belt today.'
You wear the seat belt (aside from it being the law), buy life insurance, health insurance, etc.... for the UNFORSEEABLE. I don't expect to get into an accident, die, or break my leg, but all the precautions are there anyway.
I don't forsee a crazed mad man kicking in my front door and chopping me to bits, or a crack head willing to crack my head for some silver wear, but like the seat belt, it there, just in case, never-the-less. Just like insurance.
Same reason I carry a first aid kit, spare tire, and a Leatherman Multi Tool...