When you say "There are precompiled versions of big popular binaries" - were you thinking of "firefox-bin" and such?

I think that for some years already - Gentoo has been providing binaries for "normal" packages - as long as your config/use-flags match (and if you turned on the option/flag to use binary packages).

And of course places with more than just a few Gentoo boxes were usually already running their own BINHOST setups long time ago.