Third-party GameCube controllers

Why are there so many third-party items listed under GameCube - Controllers (Hip Gear, Intec, Mad Catz…) ? I thought this website didn't track third-party products unless they're particularly valuable? What's more, most of these third-party controllers have absolutely no sales data associated with them, which make these entries pretty much useless for price charting…

On a related note, I have been wondering why the different colored controllers aren't considered variants of the same item? They do have the same model number after all (DOL-003). I would expect them to be named something like: 

GameCube Controller [Jet Black];

GameCube Controller [Spice Orange];

GameCube Controller [Indigo / Clear];

etc.