"Normal" filesystem usage doesn't generate enough stuff to require maintenance, but everyday user actions can cause little bits of stray crud like dupes, orphaned aliases, empty folders, unused plists, and the like. Not harmful at all, and using something like AppZapper will take care of the ancillary things when deleting an application, but there may still be some dross lying about.
Spring Cleaning is not a bad tool to locate a lot of little things that others don't, but again, considering the hundreds of thousandsor millionsof files/folders/apps on your system, you'd have to be pretty OC to want to spend the time cleaning every last thing out. Unless you did something really silly, like accidentally duplicating the contents of iTunes, or wildly go about adding apps that you never use (and forget what they're even for), you really don't need to do much of anything.
I do use Spring Cleaning about once or twice a year, looking for dupes, aged stuff (like hasn't been opened/launched in a couple years), orphans, and the like, but at the end of the day I clean out less than a couple hundred things taking up only a few MB of space at most. And my system isn't any "snappier" for the effort. Again, it's just how much time and effort you think it's worth.