batsbrew
why not make it usb3?
Other than using a different cable, what would the real-world difference be? RME state their products all work correctly when connected to USB3 ports (many interfaces don't) amd as for bandwidth I can run 20 24bit/44.1KHz mono inputs into Sonar and monitor several of them via track echo with plenty of USB2 bandwidth left over.
batsbrew
still haven't heard a good argument against it...
There's no compelling argument for it either. Compatibility with USB3 sockets is an obvious must, but in terms of bandwidth there's no particular problem with USB2. Unless you want to record a huge number of tracks at the same time perhaps, in which case you're probably a commercial studio or otherwise well enough funded to run several interfaces or go down the PCI card+multiple ADAT units road.
No doubt manufacturers will eventually move towards USB3 but the interfaces would still need to function with USB2 to meet the USB spec. Though some USB2 interfaces don't actually conform to spec, which is one reason many work with USB2 sockets but are dodgy with USB3.
There's also the arrival of Thunderbolt to consider. As/if Thunderbolt becomes more commonplace and prices drop it might be better for a manufacturer to support that rather than develope an interface to USB3 specs.