> is largely just a thing that native app builders do to show off and give clients a reason to believe their $300/hour is well spent

I recall an article by Zynga (maybe in Gamasutra? Can't find it now) that talked about user retention in relation to "rewards." They said that it's essentially a pure win to make every single action a user performs reward them in some way. Not a big reward—not a "points in a video game" kind of reward—but at least a pretty sound and an unexpectedly smooth animation (vis. "magic sparkles.") These things do make a difference, and it pays (in a competitive niche) for your app to do them. Just like B2B apps are sold mostly on checkbox features, B2C apps are sold mostly on how pretty they look doing their job in the app-store video.