Why do Scottish people wear kilts? Because sheep can hear a zipper from a mile away
And what is the purpose of telling this joke relating to Scottish?
I just think it's funny (and true)
I think you are thinking of a very small subset of scottish people famous for doing such deeds. Painting a whole people due to the deeds of a few is not right. Most scottish are normal people and you should meet some of them to confirm.