Do you have any evidence that this is happening? Or is it just a hypothetical threat you're proposing?

These companies aren't operating in a vacuum. Most of their users could change providers quickly if they started degrading their service.

Are you at all familiar with the architecture of systems like theirs?

The reason people don't jump to your conclusion here (and why you get downvoted) is that for anyone familiar with how this is orchestrated on the backend it's obvious that they don't need to do artificial slowdowns.