What is it about a birthday that gets everybody;s attention? Rarity? It's not that rare considering it happens regularly once a year (and in some cases, twice). Some people don't even celebrate birthdays but they're outliers. I think American culture instills in us, a celebratory streak. I think the more excuses we have to have fun, the better, and because we associate birthdays with fun, we have to go out of our way to congratulate somebody on their age level up. So just for today, I get birthday wishes for doing absolutely nothing. Nice to be congratulated on something beyond my control.