But USB 3.0 connectors are backward compatible, so what is the problem?
The problem that Joe Consumer is going to hit is when he inadvertantly uses a USB2 cable to hook up his USB3 device to his USB3 computer.
The cable fits just fine, but it won't run at USB3 speeds: it will "limp" along at USB2 speeds and Joe won't understand why his whiz-bang stuff isn't quite so whizzy or bangy.
EDIT: this is part of the basic difference between being backwards-compatible and forwards-compatible.
Similarly, Joe has been running great for 6 months, but then buys another widget and reorganizes his stuff. He remembers most of the USB2-3 gotcha, but not all of it: he has his USB3 device hooked up via a USB3 cable to his old hub, and then has another new USB3 cable between the hub and his USB3 capable computer. It works, but it isn't so whizzy or bangy, so what went wrong this time? The hub's only USB2.
Granted, we can say that we all have previously gone through the same headache in going from USB1/1.1 to USB2, but those old USB1 cables were 'forwards compatible' to USB2 (which isn't the case this time), so its not the same afterall.
Plus we should recall that USB1/1.1 really wasn't all that popular before the advent of USB2, so most of USB's adoption has occurred under USB2, so there's not really been any changes to have to try to manage.
Even back in the days of RS-232 serial interfaces, the physical cables didn't get changed or obsoleted as protocols got faster: if the cable fit, it worked at the full speed rating of the two devices being connected.
-hh