I think it's a mix of one thing or another may be better/worse price. Or if you are picky about just what kind of burger you want for me. (I sometimes like the way their burger seems to be better than just the cheap chubs, though the big tray is more than I can usually use in a week)
I'm simple though, I pretty much only bought burger, sausages, chicken breast, rotisserie chickens (to disect and use) and now the pork shoulders. Wife won't eat seasfood/turkey, shredded meats, etc and I am horrible w/ a grill havn't owned one in a decade, so I'm a simple bitch savage. Once in a while I'll buy markdown steak or a prime rib for the holidays is about it.