I think there are two reasons. First, most people might be mildly annoyed by the ads at most, and certainly wouldn’t make a buying decision based on them. Second, it’s almost impossible for new companies to compete on both quality and price at the same time, unless they’re subsidizing the product somehow (ads, perhaps? :) or as an unsustainable VC funded business I guess). How often is it that we see a new company that can make a smartphone that has the fit and finish, camera quality, and specs of an equivalently priced iPhone/Samsung/Pixel phone?