I think they're hoping for a "sweet spot" of legalization, where the product is legal to produce and sell, but regulations prevent outdoor farming (or mandate additional security in such a way that makes indoor farming an appealing alternative).
Because of the plants' sensivity to lighting (need about 12-12 hours of light/dark) and the requirement for female plants only, around the year production is not feasible in all parts of the world. Indoor production can also have higher yield and quality and lower labor requirements.
It's also a good protection against theft and vandalism as well as preventing spreading in to the wild. There might also be legal requirements that prevent outdoors production.