You say that, until you’re one of the unlucky people who discover that cloud DBs are just cloud VMs in disguise, and those cloud VMs have network throughput limits.

A fun part of a retro at my company last year was me explaining to a team, “had all of your pods’ requests succeeded, the DB would have been pushing out well over 200 Gbps, which is generally reserved for top-of-rack switches.” Of course, someone else then had to translate that into “4K Blu-Rays per second,” because web devs aren’t typically familiar with networking, racks, data centers…

Serving static files off highly efficient, distributed CDNs is a solved problem. There's no "4K blu-rays per second" when you're talking about gzipped, highly cacheable text data.

If github has a million users visiting it per day on a FRESH cache, and all of them have to download at least 10 megabytes of text data (both of these numbers are far too high), you are at ... 0.015 "4k blurays per second". Yeah I think MS's datacenters will survive.

A single-page app is not serving "static files". It might serve an initial bundle, but literally everything after that is dynamically generated. There's no way you could serve those responses via a CDN.