and wishing you many more, happier birthdays ahead

Yeah, boy, this has been a pretty rough year for Sam, hasn't it?

I don't think that the Winchesters have celebrated any birthday or holiday for a long time, tho I agree that John may have done something when the boys were much younger

That's what I think as well. Before John was so obsessed with hunting that killing the vampire took precedence over his sons birthdays. :-(