I don’t think people often realize the scope of botting. Blizzard isn’t fighting Bob in the Basement; they’re fighting a well-equipped, well-funded criminal business that makes a lot of money off of people’s poor choices.
Bots run on complicated programs that the criminals constantly update to keep ahead of the curve. That program is what Blizzard wants to break, so it can’t be used anymore in WoW.
Just banning the account won’t break the program, and banning the account won’t stop the botter. They’ll just grab another compromised account and start again, and they have a lot of compromised accounts queued up.
This isn’t a single guy with a few accounts; this is a criminal business with tons of people whose only job is to steal information and use it to make money. Botting is the least of what they do; they also steal credit cards, bank info, identities - anything to make money, because that money is very very good.
Report any bots you suspect, but also spread the word to your fellow gamers to not become a victim of their enterprise. Losing their accounts to a botter is the least of what these people are capable of.