This is because on your smartphone all brands and all retailers basically have to make the same Gorilla Glass rectangle work.
Even if you’re a pure-play, online-only, download delivery kind of business you are not a tightly defined, discrete part of the consumer’s life. You are not in a reserved, hermetically-sealed place. You are just like the big slow CPGs because you are a part of the consumer’s overall shopping behavior pattern. When you are needed you are sought, and the consumer gravitates very clearly toward the combination of product (deliver me or download me) / brand (including no-names, upstarts, etc.) / retail facility (Walmart or Amazon or your owned shop) that works best at that time.
By delivering a superior experience and product, backed by clever marketing, David’s can become Goliath’s. But Goliath’s can think and act like David’s if they can muster the institutional will to do so.