The idea behind it per the video where they introduced it is that its a means of creators to take ownership of their own content. The idea being that if you follow creator X on youtube you arent actually following creator x you're following them on youtube. If something happens or youtube removes a video for whatever reason of they have to leave the platform then you lose access to their content.

If you're on this app you follow creator x on whatever platform they are on. So in theory it's not just an all in one app but a way to solve the youtube monopoly and make for an easy transition.

In concept I think it sounds really cool, but whether it actually is able to deliver on it's goals remains to be seen.

Who asked for this, and why?

It exists to reduce dependence on YouTube.

There are bad things to say about Google all day, yet consumers will still line right back up to use Google's video service without fail. Having that content mixed in with other sites reduces dependence on YouTube over time, as creators consider decentralizing their media presence and posting content on Patreon, Nebula etc, instead of Youtube's walled garden of Communities, Memberships and of course the channel itself.

IMO right now this app is really for people who want to support OR already are supporting creators, and are displeased with the amount of apps, bad UX and poor integration this experience entails when done outside of Youtube's platform

If that's not for you, then maybe the privacy aspect of Grayjay is of interest, where the YouTube integration allows you to control what data is associated with your Google account. Aside from those, most people should probably stick with their existing YouTube client. This app is targeting a specific kind of audience, and fits right in with Rossmann's