Why are there so many bots in wow?

I am seeing a huge increase in ppl using bots lately and what startles me is that half of them i have already reported but i keep seeing them farming all the time. Before you ask i know how to spot a bot. I always attack them and they always use resurrect sickness and never do anything. They always do the same movements. They always go to the nearest herb/ore etc.

Bots are messing with the prices at the AH and its really frustrating to see them again and again even after reporting many times. I really hope something can be done about it.