If that is true then the web does not care about SEO. And quite obviously it isn't weighted particularly hard at all (probably because there wouldn't be anything left).
edit:
Case in point, except for google.com (which itself has a terrible score of 62) I can't even find out a single google service that isn't in the reds on the pagespeed index.
> Performance is not a factor in this.
If you care about SEO, it does. Check Google's pagespeed test.