Yes, of course the programmers of the different apps have quite some influence, but apart from that, if there are more users altogether on a blockchain, business owners (investors) have a bigger pool of potential customers (my example was Steem Monsters). If the products of the businesses are paid with the currency of the blockchain (for example STEEM) that should originate in more demand and thus a higher price of the currency (at least that would seem to be logical in my eyes).