What causes bots like MassPlanner to get shut down

I'm just curious as to why tools like massplanner, instagress, or even bots for other sites end up getting shut down.

Is it because they do something illegal? Are they violating some policy and then instagram/twitter/Facebook/SoundCloud threatens to sue?

We're working on a multi platform social media automation tool and want to learn more about how this can be done without doing something so bad as to get shut down by a darn social media site.

Thanks for the advice in advance!