There is one aspect we may be overlooking - and that is the element of surprise, coupled with determination. We all need sleep and so cannot be ''on watch'' 24/7 ... the would-be assassin has the advantage of choice of time and place - this is planning as against more random.The homeowner has already proven he can defend himself....I wonder what is missing in the primitive part of their pea brain to make them think they'll succeed where their homies failed.
There are many possible scenarios including long range rifle, drive-by ... arson ... child kidnap/murder. The permutations are many and scary. I'd not want to feel I was having to watch my back (and my loved ones) every second.
One situation maybe where, tho not a legal option - ''taking the fight to the enemy'' must cross the mind of someone under sustained threat - which of course presupposes they are aware of the threat and its degree in the first place. A threat could even be suggested as against implicit - enough still to totally spoil one's life.