I love the idea of USB-C: one port and one cable that can replace all other ports and cables. It sounds so simple, straightforward, and unified.
In practice, it’s not even close.
USB-C normally transfers data by the USB protocol, but it also supports Thunderbolt… sometimes. The 12-inch MacBook has a USB-C port, but it doesn’t support Thunderbolt at all. All other modern MacBook models support Thunderbolt over their USB-C ports… but if you have a 13-inch model, and it has a Touch Bar, then the right-side ports don’t have full Thunderbolt bandwidth.
If you bought a USB-C cable, it might support Thunderbolt, or it might not. There’s no way to tell by looking at it. There’s usually no way to tell whether a given USB-C device requires Thunderbolt, either — you just need to plug it in and see if it works.
Much of USB-C’s awesome capability comes from Thunderbolt and other Alternate Modes. But due to their potential bandwidth demands, computers can’t have very many USB-C ports, making it especially wasteful to lose one to a laptop’s own power cable. The severe port shortage, along with the need to connect to non-USB-C devices, inevitably leads many people to need annoying, inelegant, and expensive dongles and hubs.
Marco is right on the money on USB-C.