Running a local client (through a browser inteerface to abstract complexity) is very different than using a browser extension + someone else's server and client to talk to a relay. You can't get banned from a local client is a key differentiator.
Discussion
Another point is that it would enable abstraction to be able to run may different local clients that mimic various different socials that appear like web links, which is familiar to the user. I imagine it could be the default opening page with a gallery type view.
I do agree they share features and functionalities though.
