It seems that the more $$$ you spend on CO, the more likely you are to be selected for a promo. I have a silver colleague who travels on CO only three or four times a year, but in paid F or BF every time: once or twice DCA-SFO in F, once to HNL in BF, and maybe another HNL or DCA-Europe paid BF. He has repeatedly been chosen for promotions while another plat colleague has not. My plat colleague flies about 80k on mostly mid-range and lower Y fares. Both qualified for the most recent Mileathon, however. If you're a run-of-the mill, T class-flying silver, chances are CO isn't going to let you in on the promo action.

I wouldn't expect complaining to be very successful with respect to this issue.