Think about gaming in VR. You might want to make a game where the ML can adapt to the physical peculiarities of a person (think like personalized audio for airpods) but want to guarantee it isn't giving the person an advantage. Even simple things like setting up a VR system (or any physical computing device) can give an advantage to someone if corruptible.

At the moment there are lots of "anti-cheat" technologies that attempt to solve this, but really it needs trusted execution.