Triva:
Bots pay for boosts and subs. As long as the bots outnumber the players quitting over the bots, its a good situation for Blizzard. So why should they spend money to detect and ban the bots, just to earn less. Their first interest is to make money, making a good game is secondary. They only need to make the game about this good, that most people dont quit. If they are enjoying their time or not doesnt matter, as long as they pay.
The rare ban waves against bots are necessary, because they have to give players the impression they are not allowing bots and are active against them. They earn additional money, because most botters will buy new boosts for their characters. If they would ban the botters too often, they would quit once its not worth anymore, but thats not what Blizzard wants. They take the maximum profit.
Blizzard doesn’t make profit from botting, this was debunked time and time again:
Quite the contrary, they cost us an enormous amount - between the costs of fighting them, the fees that get attached to stolen cards used - and all the ill will from players. And just because we fight them, doesn’t mean they don’t come back. We...
Quick serch on the net will show You that companies like Blizzard have to pay back huge sums (eg. with chargeback), because botters pay for their subs with stolen/compromised credit cards.