Apps can hook into the Apple TV user profiles if they want, but many don't.
the developer needs to write code to detect the current profile. Most app’s don’t do this, and they explicitly ask a 2nd time. Not apple’s fault.
There are some apps that get this right. Infuse recently added support for this.
As a developer myself, I respect and understand that it's not their fault that profiles are useless
As a consumer, I don't care whose fault it is that profiles are useless.