different regions and city ?

[SimCity-PC]

what is the point playing more than one city on different regions ?
why the people created a lot of city on each of different regions, but they are not playing. each of city only have a few no. of population and still have a lot of space on land.
it is can be connected with two different city ?

[PresidentSmith609]

I am not very sure but u can connect it through roads. Supply like water and energy can be traded and transportation like airport can be used for profits. Hope so it helps u.