Does anyone know why a lot of the large restaurant chains are not in the city of Chicago?

It seems that in order to go to a Red Lobster, Olive Garden, Old Country Buffet, Applebee's, Cici's Pizza, Denny's, IHop and that new little place Culver's, you have to go to the suburbs. Does anyone know if there's a specific reason why these places won't come to Chicago?