Well if you carry it regularly, when you take it apart you will find there is lots of lint and other gunk on and around the detent ball, in and around the pivot and elsewhere. Upon cleaning and oiling it you will probably notice the action is a lot smoother. In rare cases if it gets really gunked up it can actually effect the locking mechanism of the knife presenting a potential safety hazard. Having your pocket knife close on you while breaking down a cardboard is no fun!

Kershaw leek is really a great knife.

Also keeping your pocket knife sharp is another example of it being directly maintainable and repairable. I often spend several hours a month sharpening my pocket knives though I probably have a few more than the average person.