There are a ton of different dynamics going on...
For me, it's not so much the botting as it is gaming the system. I like "stickin' it to the man" and doing something Blizzard doesn't want me doing. I always giggle when I hear fanboys say something like "omg, but that's against the rules!". They treat the official Terms of Use as if it were some sort of devine law or something, like the ten commandments. Weird... Anyway, it makes me feel cool.