Yeah, seems like just putting icons near the port, showing the supported technologies, would solve the problem just as well as having different ports, while not requiring different cables or space on the devices.
No. As a hardware designer, I can tell you that is a terrible idea. Yes, it looks clever at first sight (all of us went through that phase of thought). But then when you get the physical device and you get to use it, it is only a matter of days or weeks before you encounter many problems with that choice of design (inconvenience at best).
Even if the signals of some ports are electrically compatible, I try to use different shapes of connector for them if they are not logically compatible (the functions are fixed, not swappable). Because you can be sure nobody will always look at icons which are faint, small, can only be seen correctly under a certain angle and light, etc. Supposing you even know which icon means what. Supposing you can even have a sight of the icon and port, that it is hidden behind something and you have to try if it fits blindly.
You do not want to be called every other day because "it doesn't work anymore" because someone connected the wrong device to the wrong port :-). So for some serial ports with incompatible functions, you do not put all DB-9 ports, you put 1 DB-9, 1 round DIN, 1 rectangular (and hope they do not manage to fit the rectangular connector in the DB-9), 1 DB-25... It looks messy, shambolic? Yes it does. Definitely. But it is efficient because it is idiot-proof. And I mean a very large definition of 'idiot' which encompasses about everyone.
I can tell you about the number of times I 'plug' a USB cable into a DisplayPort or the power cable into the telephone plug because they sit in the same area and have sort of compatible shapes... I generally quickly notice because it does not fit well, but just imagine the nightmare if they were truly the same physical connectors...
I think my proposal wasn't clear: you wouldn't have a DisplayPort and a telephone port on the device, distinguishable only by the icon.
I think the point of USB-C is that the same port can support both functions, and so you don't have to care into which port you actually plug-in the cable. My proposal was just for when you were buying a new device, to make sure it supported the same technology as your existing devices - only then you would compare the icons.
You just reminded me of how I killed my first iPod: I somehow managed to plug the cable in upside-down. FireWire was designed to only fit in one way, but for whatever reason, the FW port I plugged it in to didn't fight back when I hurriedly tried to plug it in upside down.
