People use email because it’s the best communication system existing. If someone doesn’t want to change his address he creates his own self-hosted mail server. Or just use his own domain name when using email service with thord party email providers. Email system is amazing, the issues with ux are in fact minimal, almost non-existent.
Even if self-hosted email was easy, I don't find it to be a great idea.
I ran my own for a while using mail-in-a-box but ended up moving to fastmail because I didn't trust myself to maintain the setup. I need my email system to just work and that's likely the same for the majority of people.
(I validated that lack of trust in myself even with fastmail by not realizing for almost 3 days that I let my domain expire, thus causing emails to bounce with no way of me knowing that was happening)
Ok so make mastodon as easy as gmail. I can use Gmail.com or my own domain. Let me have same flexibility with my internet identity. I wish the USPS had gotten into the official Internet identity game. One place to receive legal emails, store my private keys, public keys etc. protected by law.
Too bad spammers and big corps broke that one as well. Maybe if it worked as a publush subscribe system (MQTT) instead where the sender was responsible for storing and distributing content, then the spam problem would be somewhat fixed?