I have that same question, "Why and who does this benefit?" It seems like everything runs in the cloud these days and is fronted by huge CDN's. The performance on 80%+ of websites should be really fast already due to local proximity wins (speed of light/bits). It looks like there's a megacloud provider location just about everywhere these days with more on the way.

This seems like a lot of energy spent to make already fast things just a tiny bit faster. Are there any real world estimates or projections for improvement? Like, how quickly will that Facebook page load or show those Google (ad) search results?

Things feel largely fine, yet here are more "improvements".

And once we have these gains, they will probably be lost in bloated javascript or app layer inefficiencies.