Not using the proper cable could lead also to fires, for example. We are talking about a significant amount of current. If you don't use a cable rated for that current, the cable or the connector will overheat, and possibly start a fire.

And it's not a remote possibility. It happened to me with a fast charging phone power supply and the phone, and the cable was the one provided by the manufacturer! The type-C connector at the phone side was red hot and started to melt, probably caused by a bad connection caused by dirt in the phone connector. Fortunately I was there, and smelled the burnt plastic and disconnected the cable, but what if that happened at night?

And it's not something trivial that power supplies and phones can detect, there is not a way to determinate the voltage drop in the cable built into the standard (basically all they needed to do was to add a voltage sensing pin on the connector, to be shorted with VCC at the load side, so the power supply could sense the voltage at the other side and determinate if there too much drop, but as far as I know it doesn't have it).