Eh, i think you're thinking too small here.

This whole thread is full of people saying things like, "When _I'm_ building a webapp," and "_My_ projects end up loading slowly," etc. Google is saying things like, "When 400 people are working on a web app, how can we avoid it turning into a shit show."

I think that is in the case of Facebook they were trying to solve their own use case, and in the case of Google, they saw it as a way of strengthening the strategic position of the web in general vs apps.