Right, you can get it on the very latest Macs, most of which are just rolling out now and none of which have been out for more than a year. USB 3 is old at this point; most manufacturers started shipping devices and computers with USB 3 ports in 2009. But because Intel didn't adopt USB3 until their Panther Point reference platform in 2012, Apple really didn't have much of a choice.

(Intel really, really wanted people to use Thunderbolt, even though there weren't any Thunderbolt devices available.)

It took four years from when the standard was finalized for Macs to finally start shipping with USB 3.