because the people who use and love WP have no idea what you're talking about when you say "JAMStack and headless CMS" and really don't care. It just does what it says on the tin.
But yes, there are other great and simple products coming up that will overtake - but they remove the techie nonsense even more. Carrd, Webflow, and about a million others.
really! how? every person and their dog is becoming part of the gig economy, selling their everything online and finding ways to create a newsletter or some kind of tool. who are these people without digital skills?