The only reason I could think of where somebody might do this would be if they were someplace like my uncle's house, where an old Arisaka rifle, with bayonet, is a wall decoration.... and they don't have an actual firearm handy when the BG breaks in.
In that case, the bayonet may be the way to go. I really can't think of any other scenario where it would come into play for home defense, let alone self-defense, without raising major bells and whistles.
By the way, if I were in that scenario at my uncle's house, I'd probably have grabbed the katana from the wall, and not the Arisaka. That would also be fun to explain; but I am more proficient with a sword than with a bayonet. (I know quite a few martial artists who have their cutting swords - as opposed to dull-edged swords like iai - in decorative mounts when not in use, so I could see this happening with some of them.)
Not sure what scenario the OP envisions, here.