When the bike, any bike, is in the work stand, the fork has a tendency to swing unpredictably. If the alloy handlebar bangs into the top tube without any buffer, ding. Once the tape is on, the chances of a ding, under those circumstances, is greatly reduced, in my opinion.

That said, the cloth tape does not really offer nearly as much protection as does the cork/rubber stuff(I have not built up many bikes with cloth tape), suggesting my error in saying "the problem goes away". So, with that in mind, and when working on the X10, I will add a cushion tube to the top tube, in an effort to prevent any possibility of oops.