They take them live because they sell them. The people that buy them want them live so they can kill and butcher at the same time and have fresh meat.
I'd rather go find a farmer with a corn-fed hog then ... but then folks will pay good money for just about anything these days ...
A lot are turned loose alive too. Buy a hog for $50-$100 and sell hunts for $200-300.
This makes sense ...