Why do you think there aren't many or any tornadoes in big cities?

I haven't heard about tornadoes wiping away a city filled with skyscrs or industrial areas or similar like NY or CA or TX or desert areas like las vegas, Nevada...usually areas like the countryside with vast fields? why do you think that's the case? don't look it up.I want to know your current opinions/hypothesis as to why tornadoes are prone in certain areas and not others.thanks.