Why do people hold hands?

I've never understood why people hold hands. I see many couples holding hands in public places. It's a signal that the person is saying, "Hey, look at me, I've got another human as my companion, aren't you jealous?" I also think these people are insecure, and they need to hold that person's hand because they are low in self-confidence or just prideful and showing off that someone likes them enough to latch on. However,  my children hold my hand while walking across the interstate. So there's that.