It has to be optional to remain a “Universal” spec.
If it had more requirements, it would be more cumbersome to implement and device manufacturers would come up with completely different, completely incompatible cables and ports (a la Apple’s lightning) that would cause you even more headaches.
“Universal” merely means devices with different capabilities can use the same interface. So you can use mice and keyboards (very low bandwidth needs) on the same port as a data hungry drive. That was the major innovation when USB took over for PS/2, parallel port, etc.
Manufacturers can still use low-end components on the client devices, the requirement would merely be that the ports in host devices and cables would meet some minimum specs to be able to meet USB certification. Instead of having a wide variety of possible configurations, force host devices into smaller niches so the marketing is clearer to customers. Devices would still negotiate voltages, data rates, etc as they do now, the only change would be forcing implementations into buckets.
It has to be optional to remain a “Universal” spec.
If it had more requirements, it would be more cumbersome to implement and device manufacturers would come up with completely different, completely incompatible cables and ports (a la Apple’s lightning) that would cause you even more headaches.
“Universal” merely means devices with different capabilities can use the same interface. So you can use mice and keyboards (very low bandwidth needs) on the same port as a data hungry drive. That was the major innovation when USB took over for PS/2, parallel port, etc.
Manufacturers can still use low-end components on the client devices, the requirement would merely be that the ports in host devices and cables would meet some minimum specs to be able to meet USB certification. Instead of having a wide variety of possible configurations, force host devices into smaller niches so the marketing is clearer to customers. Devices would still negotiate voltages, data rates, etc as they do now, the only change would be forcing implementations into buckets.