If the same drain has been cleared more than once, jetting is usually what finally settles it.
Clearing and cleaning are not the same
A cable makes a hole through the blockage so water runs again. Everything coating the pipe stays put, which is why it returns sooner each time. Jetting washes the pipe walls back to the material underneath.
Silt as well as grease
On James Island, older lines that take in groundwater also take in fine silt, which settles in any low spot. That is a different deposit from kitchen grease, and it is one a cable will pass straight through without shifting. Jetting handles both.
After roots have been cut
Jetting clears the fine material left behind once roots are removed, which would otherwise catch the next thing down the line.
When we will say no
Old cast iron or clay that has already thinned may not stand the pressure, which is why we look with a camera first. On a fragile line we will recommend lining rather than risk turning a blocked pipe into a broken one.