The plastic tubing acts like an anchor. When the cable tie is tightened, the tubing grips the fork/frame. Movement of the tie and the tubing is minimal if you tighten the tie up properly at installation. Although there may be some movement over time – and some stretch from the tie/tubing – on a suspension fork or frame, on a non-moving area like a rigid fork it leaves the hose very well fixed. You could put a wrap of electricians tape under the cable tie if you wanted, but, from my experience, I’d say that it isn’t necessary. Just use pliers to pull the cable tie tight and then check it every once in a while.