Why can't most people tickle themselves?

Question

I'm not saying I can, but most ticklish people can't tickle themselves.

Answer 1

as your body you will do these tickle not surprising ! and the tickle came from another skin not your own skin !!  

Answer 2

The same reason why if you hit your own knee, nothing will happen, but if a doctor does it, you leg goes up. I don't know why. There's a lot of things your body doesn't respond to unless stimulated by another force.  

Answer 3

because your brain knows before you do it that youre going to tickle yourself

when it comes from someone else your brain hasnt got a clue, so you feel tickled

Answer 4

Some scientists believe the cerebellum prevents us from tickling ourselves because it can distinguish expected sensations from unexpected sensations.

I've included some links below on this topic.