Some of both. I remember a time where it felt like every time I got a new computer it had some different ports because they kept evolving. Modem/Ethernet, firewire 400/800, keyboard/mouse/USB, VGA/DVI/Displsyport(and mini versions of some). Sure, my old computer might have had a lot of different ports, but I might never have used some of them. For something like a laptop, I think 2x USB-C on each side is good for most, plus add hubbing to larger peripherals like HDD enclosures and displays and docks wouldn’t have to be so popular.
I feel like we’re just in the middle of a good transition period. Few years from now almost everything that can will be USB-C, we’re really just waiting out the replacement of all the existing devices and their incompatible ports.