Edited for more emphasis on “bots” vs. “bugs.” Same difference, though.
Blizzard fights the good fight against bots all day, every day. You would not like it at all if they actually ignored botting or even let up just a smidge on their war against it. The game is as “bot-free*” as it is, because they constantly battle the bots.
Just like in real life - we fight crime, but some crime will always exist, forever and ever. You can go to the mall without fear of being robbed or assaulted, though those crimes do exist in some places right in the city you live in.
*Yes, bot-free. There are like 250 servers, amounting to something over 10,000 total zones. Are there bots in 100 of them? Sure. But that also means there are like 9,900 zones game-wide that are bot-free. You gotta look at the whole picture, not just one pixel.