The USB protocol was simple by design, so it could be implemented in small dumb devices like pen drives. More specifically, it used two couples of cables, one couple was for power and the other for data (four wires in total). Having a single half-duplex data line means you need some way of arbitrating who can send data at any time. The easiest way to do it is having a single machine that decides who gets to send data (master), and the easiest way to decide the master is to not do it and have the computer always do the master. This means you couldn't connect two computers together because they would both try to be the master.

I used the past tense because you may have noticed that micro USB have 5 pins and not 4, that's because phones are computers and they use the 5th pin to decide how to behave. If it's grounded they act as a slave (the male micro to male A cable grounds it). If it has a resistor (the otg cable has it) it act as master. And if the devices are connected with a wire on that pin (on some special micro to micro) they negotiate the connection.

When they made usb 3.0 and they realized that not having the 5th wire on the usb-A was stupid, so they put it (along side some extra data lines) that's why they have an odd number of wires. So with usb 3 you can connect computers together, but you need a special cable that uses the negotiation wire. Also I don't know what software you need for it to work.

Usb-c is basically two USB 3.0 in the same cable, so you can probably connect computers with that. But often the port on the devices only uses one, so it might not be faster. Originally they put the pins for two connections so you could flip the connector, but later they realized they could use them to get double speed.