I can't give a profound ad-expert explanation, but when I land on an app, my decision to install it or not depends on the reviews/ratings.
Your app has only 2 reviews visible (I can't confirm they are the only reviews) with 4 and 5 stars. Really not bad, but unless a review clearly says it's better than bloomberg, stockwatch and whatever, I would still classify your app as just another one.
AND, this is also a big point, human inertia is also a factor, if somebody already use a stock app, the tendency is to stick with what they already know.
But you're really on the right track, as you're getting their attention. Maybe you're just missing a deal-maker somewhere, an intangible...