Come on, it's only a plastic cable, how it can ruin the paint on my bike?
It can!. And yes your thinking is logical and common sense, but physics show us it's more brutal face in cases like that: On a mountain bike, where lots of vibration happens (more the faster and the rougher the trail and your riding style is), the brake, shifter, or post cables, even when made with soft plastic, rub, peel, destroy your bike paint, and even the metal.
It's weird, but a plastic micro-impacting and vibrating at high frequency can severely damage your bike paint, and even the aluminium, carbon or steel material itself.
Have a look at the images below to show it:
Also your shoes wear the paint. Have a look at this swingarm:
And how to solve it?. With another plastic. This is one of the main functions of our AMS Frame Guards made with PVC plastic, that will keep your bike as new as first day.
And what happens if it's already damaged? Protect and cover it with a Colored Frame Guard: