Users need interactive stuff. If your site isn't interactive and your competitor's site IS interactive, customers almost certainly will prefer your competitor.

When you try to chain that stuff across multiple backend-rendered pages, you get a whole other list of problems. If you need to track all the otherwise transient UI stuff on the BE, you have now created a whole mess of stateful APIs and turned horizontal scaling into a much bigger issue than it needed to be.

Users wants something that will help with whatever they want done. And the quicker, the better. Interactivity is nice, but I never seen anyone complains about multipages applications.

> If you need to track all the otherwise transient UI stuff on the BE

So don’t add transient stuff? You send a page or a form according to the URL, the user does whatever it wants and either request a new page or submit the form. Each page is standalone like activities in an Android app. Anything transient is taken care of on the client side.