These are the 4 agencies you have to pay royaltees to.
I've seen the rates. Altogether it's about $6k per year to stream your standard shoutcast style station. When streamers like spotify, etc have revenues in the millions, that's a drop in the bucket.
The only time there is a sabot in the gears is when it's video. Then your standard mechanical/compositional licenses fees are required, and on top of that a Sync license is required which adds an entire clusterfuck of problems. With non-sync you just pay the 4 agencies, but none of them collect Sync rights. You have to track down every person involved in the production to get permission to stream any music with video in it.