Three main reasons for running your car...
1. To get oil circulating through the system. Oil safely settles in the bottom of the engine when not in use but most parts on a engine are designed to be lubricated/preserved via this same engine oil. The seals on various parts in particular.
2. To get gas circulating through the system. If left alone gas turns into a nasty shellac-like substance, particularly the small deposits found in the carborator. There are preservatives you can add to keep the gas in the tank from going all nasty, but it doesn't help residual gas left in the lines and carb.
3. To keep the battery charged. Car batteries weaken while sitting around just like a normal household battery does. You don't notice this when you are driving it regularly because your alternator is doing it's job, but letting a acid core battery drain completely via lack of use can shorten it's life span.
Now if I only practiced what I preached.

I'm guessing small scale electronics have similar issues, but disc drives don't really use oil, so that isn't it. My guess would be that springs and rubber parts lose their tension, but then again they would lose their tension via excessive use as well, so I dunno how you could prevent this problem.