I didn't go home for my sister's birthday as I'd only moved out about a month ago and I wanted to settle in properly. We spoke on the phone though and I think I skyped her.
However I'm surprising my mum by going home on mother's day. We're quite a tight-knit family so for us I think it's just a normal thing that we want to be together on whatever occasion. I know not all families are like that though so I guess it just depends, I wouldn't say it's like a rule that you SHOULD see your families on these occasions, it's just about what you want to do surely.
Edit - A lot of people saying they wouldn't for something like mother's/father's day, probably worth pointing out that I had planned to surprise her on her birthday but then realised it would be the easter holidays anyway!
Luckily I don't have this problem as my little sister's birthday is during the Christmas holidays. I'd go back anyway though, she'd be gutted if I didn't, especially as she's a lot younger than me. :3 We're a very close family, though.