The bots can avoid this by staying low impact. Farming data for AI training is rather simple. Vote brigading is also hard to track.
In the same way advertising is money spent hoping for revenue, shaping the visibility of posts by your actually human coworkers and customers work similarly.
Bot presence isn't the problem, the issues caused to the community by a high volume of scraping and spam is. Bots staying low impact and not being annoying enough to get banned is almost as good as eliminating them entirely, unless you're a perfectionist.
In the same way advertising is money spent hoping for revenue, shaping the visibility of posts by your actually human coworkers and customers work similarly.