A cable or snake is built to punch a hole through a clog and get water moving again, but it doesn't do much for what's left coating the inside of the pipe. Grease, soap scum, and mineral buildup can stay stuck to the pipe walls even after a snake clears the immediate blockage, which is part of why the same drain tends to clog again a few months later.
Water jetting works differently. High-pressure water sprays in every direction as it moves through the line, scouring the full circumference of the pipe instead of just punching through the middle. That means it clears the clog and the buildup that caused it, which is why jetted lines tend to stay open longer than lines that were only snaked.
