system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can I not plug a double ended USB into 2 laptops and just transfer files across?
gpt
Because USB protocol follows master-slave convention. One device is "ruling" USB bus and other devices must follow. If you connect two computers that way, both would want to be "masters". There is also electrical problem, because both PC are providing power to 5V lines. If that circuitry is badly designed it could just fail when there is voltage from the other side present.

There are however special USB cables designed exactly for data transfer. They act like external network card.