I don't think that "this is bad software because I am not yet the target audience" is a good metric for measuring the worth of a product.

Well, it's an excellent metric of measuring the worth of a product for the only "market segment" that matters to us. That is, us.

Second, intentional coverage just goes with the domain for a flights application. Are Americans supposed to just switch back and forth to some competitor for non domestic flights?

By that logic, all of the startups that begin only serving their local market (many start in SF and expand beyond once it's viable; true in many other locations as well) would be 1/10 or 2/10.