Stripping removes debugging symbols and such junk. It makes them smaller, faster, and require less memory. However, if they crash, you can't really figure out why. If you're a developer and need to debug your stuff, you wouldn't want to strip. If you're just a user who wouldn't debug something or even know how, might as well strip.
You can strip libs, too, but this sometimes has more negative effects. Not sure of the details there. A guru can maybe clarify or correct me if I'm altogether mistaken but this is my understanding.