Because there are a zillion things other than USB drives that people plug into those ports. Phones (both to charge and occasionally to sync), headphones, 2FA authenticators, cameras, gamepads, printers--the list is long and it isn't getting much shorter over time.
The thing is people will plug their printer in there because it's the first slot they see, then the cable management will look really bad and ruin the industrial design the PC maker wanted. I'd like to see a Mac Mini/NUC with a Qi charger on top to charge a phone.
Most 2FA USB devices do not support NFC to make them wireless. Even if you do have an NFC enabled 2FA device, Macs don't have NFC. So, wireless is not an option.
