Nobody is going to invest money in something expected to be an alternative 30 years from now. The developers hope there is current demand for indoor skiing.
Where is indoor skiing most successful now? I think mainly in Euro ski markets that are not easy driving distance to the Alps, such as England, northern Germany, the Low Countries. My guess is that usage comes from beginners and some people practicing for their one week vacation in the Alps.
EMSC and James' references above comment that indoor is not so different from some places in the Midwest or Southeast and often more pleasant considering crowds, weather and surface conditions. There are times it will be more pleasant than Mountain Creek, the Poconos or the Catskills too. As with other "molehills," I think terrain parks may be a big attraction. I'm guessing it's still too short for much in the way of racing.
If I were picking a location for indoor skiing in the US, I'd choose a big metro area far from real skiing like Dallas or Atlanta. OTOH NYC is by far the biggest metro area, so only a tiny slice of its residents would be enough to make Big Snow successful.