It's because decentralization freaks normal people out and they desperately just want to be told where to go. The single, uniform product paradigm is very comfortable and understandable — we had to meet people where they're at.
The option for other servers is great and important, but when we added the big “Join m.s" button to the app (in addition to the server picker flow), we saw far less falloff from people who would've just written Mastodon off altogether otherwise.
https://mastodon.social/@taylorlorenz/113339615131367067
@taylorlorenz It's similar to politics. You’re rarely gonna get to exactly where you want (a perfect candidate or, in this case, users spread out uniformly based on an informed server decision), but some progress is better than nothing at all. You vote for the candidate that gets closer to what you wanna see and you design the experience that gets closer to the outcome you wanna see (in this case, ushering people the fuck away from Twitter rather than letting them say "this is too complex, nvm”)