Hmmm... I'm not following you -- what route are supposedly passive cables using to limit the current? Or are you saying they're not actually passive cables???
There are 4 pins (and wires) on a USB cable. The 2 outer pins are for power (+ and -), the inner 2 are for data (tx and rx). All USB connectors have a circuit board. If the data pins aren't looped, the board defaults to whatever it's programmed for (100-500ma usually).
The USB cable has a spec that isn't always followed, especially the cheap cables from China.
Here's an older USB-A connector w/o the plastic molding around it (newer ones are much smaller).


