USB-A requires some force to be plugged, and most users are "gentle" when plugging (not using too much force). So what happens is, the user tries it first in th

USB-A requires some force to be plugged, and most users are "gentle" when plugging (not using too much force). So what happens is, the user tries it first in the correct orientation, but it doesn't enter (because the user was too gentle). The user flips to the wrong orientation, and uses a bit more force (but it won't enter because it's upside down). The user then flips back to the first orientation, and uses even more force; this time, the force is enough, and the plug enters the socket.