Public sites need to load quickly and use progressive enhancement, work without JavaScript even. Next.js is driving this with server side rendering and hybrid approaches. They've done a great job so far.
Then there are applications that have a browser UI. These typically use a JSON-based API (REST, RPC, or GraphQL doesn't matter). These apps don't require server side rendering and their API backend can be anything.
In the latter model, you just host a bunch of static assets and point them to your API. No need for compute, everything is done client side (except API operations of course).
In the first model, you need to pay for rendering and it guides you into doing the API the same way. Closer to older PHP/ASP sites but on steroids.
This move caters to Next.js. IMO, as a lot of recent developments do.