Adding a binary package host allows Portage to install cryptographically signed, compiled packages. In many cases, adding a binary package host will greatly decrease the mean time to package installation and adds much benefit when running Gentoo on older, slower, or low power systems.
I’ve always wondered what the use case for Gentoo-but-binary is. I’m sure there is one, I just can’t think of one.
Lazy people who wanna pretend they run gentoo? Dunno either…