It depends, but like others here, I think it's because of childhood issues. I was obligated to hug all of my family members during visits, which meant I regularly *had* to hug the person who was molesting me.

If I'm really close to someone, especially when going through a difficult time, I want *some* hugs. I like a hug now and again, but I'm not really a cuddler or overly affectionate. If I haven't seen someone I care about for a long time and then see them again, I will immediately reach for a hug. If it's my son and he wants hugs though, that's a whole different story. He is just walking sunshine.