While this is scummy to do, Twitch doesn't actually care about this at all. A month or two ago, a well known CS GO streamer was caught doing it. He isn't well known because he is good at the game, he isn't well known because he's a pro, he's well known because the thousands of fake views he gets catapults him to the top of the list.

Well a month or two back someone made a post on the CS GO subreddit about him. It hit top of the front page, many people saw it. The user that posted provided all kinds of proof, such as graphs showing how the streamer's viewer numbers shot up by the thousands in the matter of a minute and compared that to many graphs from popular (legit) streamers that show a gradual increase in viewers.

You know how this streamer was dealt with? Not at all. If anything, the publicity helped him get legit viewers.

The fact of the matter is, as you described, it's extremely easy to tell these bots from real people. Obviously Twitch could do that with ease. They often follow either 0 people, 1 person (the streamer in question), or some arbitrary number that's the exact same between all of the bots (the customers that purchase these services).

A reasonably popular CS GO streamer, Cro, was caught when he accidentally showed both an email from a service like this he paid for on stream and then the page open in a browser. The page open and an emailed receipt...you pretty much won't get any more proof than that. Twitch gave him a temporary ban and he was unbanned within days.

Twitch is adding additional revenue by allowing these channels to exist. Twitch wants people to get popular by any means so that their organic views grow and they get more subscribers, thus making Twitch more money.

This is a scummy thing to do as streamers that work hard and put the time in should be rewarded.