I struggle to remember birthdays, usually. Not because I don't care, but because it's difficult for me to have the prudence to remember one particular day in the year. I leave myself notes about people's birthdays too sometimes, but even then, I forget, since I completely forget about the note until the person's next birthday. It makes me feel guilty sometimes, to be honest!
I don't celebrate my birthday beyond maybe buying some ice cream, so I don't mind it when people don't remember my birthday.