Why doesn't it tickle when you tickle yourself

I saw this question on a commercial and now I am kind of wondering it.

Well it's because when you tickle yourself you KNOW that your tickling yourself its like this grab a ruler hold on in hand above the other one make your hand so you can grab the ruler if it falls from your hand okay then let go the ruler and catch it with the other hand see you grabbed it really fast it's because your brain sends signals to you arms or something but your brain tells your body to grab the ruler so I hope it makes sense

Because the whole reason why tickling tickles is because you didnt expect it. If you do it to urself, u expect it