You don't really "compile stuff yourself" on Gentoo. There's still a package manager, and it does all the building and installing for you. Yes, compilation happens as a result of the user invoking the package manager, but there's a huge usability difference between "emerge foo", and download foo.tar.gz -> unpack -> configure/build/install -> track updates and repeat as needed. I would call the latter "compiling foo yourself", but not the former.