It’s always about the money. USB A ports are either really cheap, or manufacturing the enclosure with the same port on both sides is cheaper. Could also be that the enclosure is a reused enclosure...
I don't understand how that's cheaper than the alternative of paying a few cents more for the correct receptacles and then not even including cables, because the customer can use literally any standard off-the-shelf cable.
And also in more recent years, Intel DCI uses A-A 3.0 cable for CPU debugging on tablet PCs. Lesser known but Intel defines USB host controller spec.
So not allowed in spec for public use, but not custom cables per se.
So, I'm mildly confident you're right about A-A cables being valid, at least at some point.
https://images-na.ssl-images-amazon.com/images/I/817dK2e-q9L...
Those have a dongle inside the cable to actually do something useful, versus mindless delivering 5 volts to the other end.