I agree that the good ole stateless HTTP protocol is great, but the thing is, as soon as your web page is simultaneously displaying content from two separate HTTP requests, your web page itself is maintaining state. That's very evident on complex single-page applications like an email, chat, or calendar app, but it's also true even if you load static HTML from a server then have a bit of client-side JavaScript that checks authentication status and shows the visitor's profile picture in the top bar if they're logged in. That's a pretty basic technique that web developers have been doing for probably 20 years, yet it already requires tooling and/or developer thought to manage what is now a stateful computing session.