Why does most Arduinos use USB B connectors when USB A to USB A cables are so common?
I don't think so. Male to female USB A "extenders" are
moderately common, but the A to B "printer" cable is definitely more common.
PCB mount male "A" fittings are used on things such as the USB to TTL adapters, essentially because they tend to resemble a plug and
some of the time, it is possible to plug them directly into a PC or hub port. That is not always practical and extenders often have to be used.
Now I
do hope you are not suggesting the fitting of a USB
female connector on a board - as is done on the common
"Breadboard Power Supply" modules because this is quite simply against the USB standard.