Probably because a shiny Golurk looks epic as all get-out. I mean, that coloration is just plainly awesome. But in my case--it's a Golett. That's grey and black and cute all over. So I need the little cutie-pie like I need air.
(I told you I shouldn't answer this!)
Am I the only one around here who feels a little guilty for catching Pokemon that will only be used as tossers? I've caught around 20 in B2 and all they've done is end up on Black and released. It seems kinda cruel to do that to them.