Technically USB A male-to-female extension cables are also forbidden, at least in terms of USB 1/1.1/2.0 and were never supposed to exist. That's not to say that they didn't, because they certainly do, and sometimes even manage to work in the process. But the original USB spec specifically envisaged that a passive extension cable should never be available to the consumer, probably for the simple reason that the maximum allowable cable length was 5 meters with no ifs, ands, or buts. And USB 3.x is only 3 meters. If allowed, people would inevitably daisy-chain so many cables together that their connected device would stop working, and then whine at the manufacturer/retailer/Microsoft about it being "defective," so this was nipped in the bud in advance.

All that said, I have nevertheless accumulated about 20 of the damn things over the years in varying lengths and levels of quality. I have violated the official cable length spec with impunity and more often than not gotten away with it, albeit usually only for low-demand devices like keyboards.