A big part of this is that people were concatenating XML together manually, to predictable disaster.
Nowadays they use JSX and TypeScript, far more strict than XML ever was, and absolutely love it.
And we're already moving away from that, landing us into HTMX/hypermedia and other fancy tools which aren't really concerned with JSX. So things come and go, but standards stay to keep things working and options available for people with different constraints. It's not up to Google to be deciding all that just by themselves.