Sending a personal message on someone's birthday shows that you care about them. While internet cards might be fun, an honest-to-goodness card that comes through the mail is still a special thing to receive.
But all of us get busy and may not live next to a shopping mall where you can find a variety of greeting cards that will please the special birthday boy or girl. Even if you do live near a store that sells cards, you may not have the time to pick out a card every time you need one. That's when an online source of cards can be handy.