and once a botter gets going, has a good handle on creating their own profiles, there is little reason to come back to the forums. many of us here frequent the forums because we feel we have something to offer to the random poster. whether its help with a simple 'hey delete your settings folder' or maybe post a ban report. or maybe just bored and looking for a quick conversation.
i could even go as far as saying many of us regulars you see here are so casual we could go days without botting and not miss a beat.
i play on illidan from time to time, we have 220k+ players on horde side. i know quite a few people who bot there. out of the very very small percentage of players i play with on illidan, a large percentage of them bot. its random, i dont go hunting down people asking if they bot, i dont care to chase friends on wow. they just show up.