I haven't done a clean install of OS X in a long time, but I'm pretty sure /usr/local/bin exists. But even if it doesn't I don't find this a compelling argument. Having /usr/local/bin owned by root is a universally accepted standard in the unix world, and with very good reason: having /usr/local/bin owned by a user introduces security risks.
/usr/local/bin is a global resource. It is generally full of binaries that get run by many different users including root. If a regular user can replace those binaries the result is a privilege escalation.
Well, by default /usr/local/bin is empty. But people commonly install things there that eventually get run by root. The most obvious example is various programming languages, different versions of Python, alternate shells, etc.
