Polishing a bike is a lot harder to do properly, because of all the bits hanging on it and the lack of surface area. The only way to really do it right it to polish a bare frame/fork. Otherwise you're just polishing around bolt-on's and either missing spots or leaving residue.
Cares do not have stuff hanging on them all over the place, and they have large surface areas that lend themselves very well to efficient polishing.
Plus, bikes are not subjected to nearly as much finish abuse as the average daily driver car, so they need to be polished much less frequently - if at all. They don't rack up the mileage cars do, they don't get subjected to the same adverse conditions for similar time periods, and they don't sit out in the parking lot all day every day while you're at work.
"Love is not the dying moan of a distant violin, itís the triumphant twang of a bedspring."
S. J. Perelman
Last edited by bigbossman; 12-03-10 at 07:08 PM.