We’ve had the standard USB plug (USB-A) in widespread use for 18 years, and it’s going to take a few more years for USB-C to become so ubiquitous that we can get away without USB-A ports most of the time.
A pro laptop released today should definitely have USB-C ports — mostly USB-C ports, even — but it should also have at least one USB-A port.
This may have been the more pragmatic approach from Marco’s perspective, but it all depends on what Apple was trying to accomplish. Maybe Apple was determined to push the industry towards USB-C and wireless as quickly as possible. If that’s the case, including a USB-A port would have been detrimental to their plans — prolonging the lifespan of a dying technology.