Sometimes these kinds of touchy people can do bad..
They spread germs with every single tap on a shoulder. These germs can possibly land you with a dangerous disease. A lot of diseases can lay dormant for years before they show symptoms, the "touchy person" may not know they have it and has given it to so many people already.
Keep touching to a minimum with your close friends...
Or don't touch each other at all!
The Spread of Germs
So many germs and bacteria are already on your skin, adding more might not help anything.