I have purchased handguns for these reasons:
EDC (every day carry)
My G29. Wear it all day long and shoot at least 50 rounds through it on every trip to the range, just to stay nice and familiar with it.
less expensive carry to be locked in the car when I'm not allowed to bring it wherever I'm going
No, really -- for places like sporting events or school functions where it's not legal to carry, I still want the carry gun along... but it would break my heart if some schmuck stole my G29. So my Ruger P95 is perfect for this role.
pure paper punching joy
I've got a number of these... just a joy to shoot slow fire and try to make the smallest sized group I can manage.
pure "bottle filled with water" shooting joy
I love to shoot at things that actually take & show damage. Only ever do this at my private outdoor range (at a buddy's place) but have a blast doing this. Great thing is that any handgun works here!
hunting handgun, even though I've been hunting like 4 times in my entire life
Picked up a .44 Mag barrel for my Contender to address this. It's a MF'er in recoil, though, so I hardly ever shoot it.
home defense
In this role, I like my S&W 1006 for a number of reasons.
gotta have something to handload for, since I have these dies and brass here...
Yep -- that was the express purpose for buying my .30 Carb Ruger Blackhawk and it has become one of my most enjoyable handguns. I had the dies, three boxes of bullets and a small supply of brass that I hadn't used in 15 years, so I needed a firearm to make use of those tools & components. So I bought the Blackhawk and it's been pure joy to shoot and serves no real purpose. It makes a horrendous noise, concussion and fireball but without a lot of recoil. The bullets don't cost much. The thing is supremely accurate, though the long 7.5" tube is a bit unwieldy. This revolver is even at home at 100 yards and I can't do much with most of my other handguns at 100 yards. (outside of the Contender, that is!)
Probably some reasons I forgot!