I own partly because I hunt, partly because I collect, mostly because as someone else said, it is the right which secures all other rights, and partly because of defense.
Home defense? My pistol (locked in a bedside finger safe) which will get me to my M4. A .45 firing federal HSTs will tend to not maintain a lethal velocity after going through two layers of dry wall. My M4 because it is what I am most comfortable with, and it has good terminal effects on target without over penetrating. Also, it does not do a good job of penetrating walls and what not at close ranges because it tends to yaw and break up.
Shotguns are good, if you run the correct ammo. They are big and scary, and the sound of racking a round will generally send most people packing. But buck shot will tend to not punch through to vital organs at fairly short distances.
That is number four buck from a twenty inch barrel at 3 meters. We know from testing that you need to have at least 7 inches of penetration in gel to hit vitals from all angles, and through bone. They will leave a mess, but if someone is on something, it may not put them down. BUT, a shotgun is better than nothing, and it is easier to hit the target with a shotgun than it is a pistol. Definitely better than simply hoping no one breaks in.
It is a thing that you will not understand unless you are a gun owner. I have had firearms my whole life. I was taught to respect them (not fear them) from an early age. If you were not exposed to this, then odds are you fear them because you do not understand them. Fear never solved anything.