Need implies a lot. You can be needy and that is generally a bad thing. But it is ok to have needs. The human body has them and there is nothing that can be done about it. I prefer to think of this as something that I cannot live without... something essential to my life.
I once read or heard somewhere that in order for someone to feel happy they need something like at least 30 touches over the day. Doesn't have to be hugs or something big, but just to be in physical contact with someone else. That stuck with me for some reason. You might notice in your own life how often you touch someone else... and if you find a lack of someone else... do you notice how many more times you touch your own face, head, arms etc. Even now I find that I am sitting so that my feet are both touching each other without realizing it.
A "headpet" is common around my house. It is calming and loving. I never used to believe that notion that having a pet would lower your blood pressure; I do now.
It must be something comforting, reassuring that we need to do... or at least I think so.
Just as an aside, no one pets John's head, it's not manly. :P