Apple software doesnt have all the dependency issues that Windows has and also doesnt have .dlls strewn all over the place (as well as all the entries in the registry), since it keeps the the bulk of programs in packages. Preference files and the like dont take much space, so they can be left alone, unless one really feels the need to remove all traces of a program. So, uninstalling a program with Apple merely requires deleting the program for all intents and purposes.