A (rather poor) analogy of how I see it... [non Tag-based]
1.) Someone gives me 100 bins. Each group of 10 bins is painted a different color. Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, and White. Each bin in the group has a number from 1 to 10. I will have NO trouble organizing my parts into these bins, and I will easily remember what parts are in what bins...
2.) Someone gives me an unlimited number of bins, and I can paint each of them any color of the rainbow. Now I can't even get started...