All right, you ready? I'm about to blow your mind.
It's actually not pumpkin flavoured at all. It's a mixture of spices that's supposed to remind us of pumpkin pie. We could actually probably make it ourselves whenever we wanted, but because it's only "released" during the fall, it's "limited" and people go nuts over it. Like peppermint at Christmas.
Supply and demand, bro. Nothing special, just really good marketing.