Why don't more people use XMPP?

XMPP is not normie friendly. I understand why everyone in the privacy community hates Signal’s insistence on using phone numbers but the ease of use of doing so for most people is why Signal is so popular. They just have to download Signal, then allow access to contacts and they’re good to go. You can of course (and should) harden it further but you don’t have to in order to start using it.