I'm not sure of how everything works but one thing I've been wondering is about mint incentive structures. Do they have incentives to behave well? 

Why would a mint rug it's users? Why not? Isn't there's great economic incentive for them to do so?

Minibits is one exception I can think of. Why would Minibits' mint rug us? They wouldn't, because they make a great cashu app and rugging us would destroy their reputation and their app's userbase.