But seriously though, if you start to make it more distributed than it already is it will look even less like Twitter.
They just want to sign up, and get an out-of-the box experience more or less like twitter.
Mastodon is built so that there is no single point of failure, but that means users have no single point of signup. It is like email, or matrix. Host your own on your own domain for a few dollars a month or join a friendly server paying the bill for you.
It is really not that hard, but people are just not used to having choices on the internet anymore.
At some point someone you know picked Twitter and you did too. Maybe find some friends or public figures you like on Mastodon and see what server they are on.
It's more like if someone asked why they need to choose between someone@gmail.com address or someone@outlook.com, but in reality email would work just fine regardless.
EDIT: fixed
You are forced to chose because there is not a central blessed server that acts as a main hub.
In Mastodon you can choose a french server if you are french and agree with generally accepted french values of moderation, or you can choose a general purpose server, or host your own.
There are a lot of LGBT servers and special interest servers with strict moderation, and general purpose servers that moderate very little.
It is also a bit like choosing what city to live in... except it is -much- easier to move if you decide you do not like the vibe and wish to live somewhere else. Mastodon has built-in user forwarding to take your follows and followers with you.
How do I "participate across the fediverse" without creating one account per server? Is there a part of the UI I just haven't stumbled on yet?
Similarly servers do not share credentials, but you can follow people no matter what server they are on.
there's a lot of chicken & egg issues still going on. I think it'll get better as more people put their info on their web pages, though.