We’ll obviously people are finding / needing a use for a service like this. Paaster has 340+ stars & a similar project Privatebin has 5.1k stars.
Sometimes you want to share data briefly with others or to only a specific groups of people (private forums, game lobbies etc) so being able to do so quickly and securely can be extremely useful.
Also this is a privacy page, why should your Pastebin data be stored in raw text and easily indexable by the host? Obviously pastebin data has the potential to be sensitive (look at the amount of people leaking things on pastebin.com)
Also data leaks do occur! Why should all your pastes be publicly viewable when you only intended to share it with people XYZ platform etc.
The fact your unable to imagine use cases and benefits of such services / projects honestly amazes me.