There is a lot more to opening a store there than just having an available location and potential customers.
Like everything else in the world, there are politics. And of course logistics. The existing NY kosher distributors will not travel 200 miles out of their way just to deliver to one store. 7 Mile Market has their own truck(s) that bring them their stock. You can be sure they are not offering to share it with another store. And local distributors in Maryland already have contracts with 7 Mile Market that would be put in jeopardy if they agree to service their competitors.