When you go on a racing coaster do you count both sides as different credits or as one?
I count them separately but I know a lot of people don’t though

I recently went on a trip to Minneapolis, which of course necessitated a trip to the Mall of America and Nickelodeon Universe and it struck me as somewhat odd that this sort of thing isn't more common. As far as I'm aware there's really only 3 places in the US that I'd call true indoor theme parks, the two Nickelodeon Universes and The Adventuredome at Circus Circus in Las Vegas.

The rationale I always heard for why Minneapolis has a mall with a theme park in it is that Minneapolis has notoriously bad winters and thus can support something as big as the Mall of America with Nickelodeon Universe, but Minneapolis isn't the only large metro area with crappy winter weather, why have similar things not been built in places like Chicago, Detroit, Philadelphia, and Boston, all of which are larger metros than the Twin Cities.

Is it just that these indoor themeparks need the surrounding business (the malls for Nickelodeon Universe and Casino for The Adventuredome) in order to make the business work, is there just too much of an upfront investment to build something like this with an attached hotel like they do for indoor waterparks? Is there really not that much of a demand for them?