Presumably enough to make it worth Apple's while to implement the option under an umbrella entitlement over tools that may help support perhaps flagging self-discipline. Presumably too, it was worth the app dev's while to go through the effort and process of implementing the assertion. I have some mild doubts about the fundamental efficacy of such an approach, but its motivation seems clear enough.

For any more than that you're asking quite the wrong person, I'm afraid. For one, I don't intuitively understand the use case; the way this works for me is that I set my phone to play reveille when I need to wake up, and when it does, I do. That makes convenient use of some early training which is all well and good for me personally, but it leaves me little able to speak to the concerns of those for whom nothing so simple can serve.