The problem is, and was for me too - that's not how people think of email. Saying "pick a server" is really arcane for most people, even "pick a domain." The fediverse as a whole has a terminology and jargon problem it still hasn't completely reckoned with, or at least figured out.
We have very different perceptions of how people approach emails.
Guess how tech illiterates(?) approach email? They sign up on Gmail - perhaps with some handholding - and that's it. That's all they know or care about.
And before you say they don't deserve to be on the internet: they are all using Facebook, Youtube, Whatsapp, etc. Unless platforms like Lemmy actually treat new users better, there's not much incentive for people to switch.