6 Answers

....reminds me of a little saying we used in elementary to gross out the girls:

....you can pick your friends and you can pick your nose but, you can't 

pick your friend's nose !

Let's see, they have hands with fingers. The nose is an orifice as is the mouth and ears. Kids explore as they can...

Kids pick their noses because "it works", same as you and everybody else.  Just because you can't "see" it doesn't mean nothing is there.  You've blown your nose enough to know you don't wait until stuff is dripping or crawling out. 

I Could never do that as a kid,my fingers were to fat,had to get another kid to do it for me,,

They do it b/c it's something to do . 

In 1989 Blancpain introduced the last of link its six masterpieces the flying tourbillon ref. 0023. It was the first flying tourbillon link in a wristwatch developed with the help of independent watchmaker Vincent Calabrese. Oh and it was still just 8mm link thick.