Because he can. Have you changed anything heat/light/enclosure wise over the last couple of days?

My cope's grey is down to something like 2 small crickets every other/third day. Personally, I think he's pissed at me b/c I've become a stickler about not feeding him huge crickets which is what he seems to prefer, so he's just decided that he'll make me twitch by not eating. If he doesn't eat the small guys before they hit adult sized then they go in to work.