People do buy new bikes and set them up so they can ride them whenever. Having only one bike can be an advantage when space is tight. What others have said about rain grime wearing out bikes is true but most of that can be eliminated by using full fenders. There are very nice expensive bikes being made that are set up to use fenders and a wide range of tire sizes. They are usually steel. It's ironic that the frame material most susceptical oxidation from water is the also the most capable of dealing with it.