Benson Leung counts six:
Why did it come to this? This problem was created because the USB-C connectors were designed to replace all of the previous USB connectors at the same time as vastly increasing what the cable could do in power, data, and display dimensions. The new connector may be and virtually impossible to plug in improperly (no USB superposition problem, no grabbing the wrong end of the cable), but sacrificed for that simplicity is the ability to intuitively know whether the system you’ve connected together has all of the functionality possible. The USB spec also cannot simply mandate that all USB-C cables have the maximum number of wires all the time because that would vastly increase BOM cost for cases where the cable is just used for charging primarily.
Thunderbolt 3 makes this even more complicated, as it fits yet more functionality into a connector of exactly the same size and shape. USB 4 will merge the two standards, but I can’t work out whether that will make for more or less confusion.