There's a lot more to this than might seem on a quick look:
As business models go, there are currently two dominant ones: either people like your product enough to purchase it or they don’t care enough to buy it but will overlook its deficiencies if it’s “free” in exchange for their personal browsing and purchasing info sold to advertisers. The former model is Apple’s, the latter is Google’s.
Apple sells emotional experiences. The price is what users pay to be delighted by Apple’s stream of innovations and to be free of the lowest common denominator burdens and the pervasive harvesting of their personal info.
Google sells eyeballs. To be more precise, the clickstream attached to those eyeballs. Thus scale, indeed dominance, is absolutely crucial to Google’s model.
The weight of scale
Android may be a lackluster clone of iOS in terms of UI and fluidity, but as an economic proposition it’s nothing short of an extension of Google’s desktop/online business model. Google’s model wouldn’t work with something like 20% market share. If a market is highly fractured among smaller players, business models like Google’s that rely on massive scale wouldn’t work well. As with Microsoft’s Win32 API or Office formats, scale is erected to beget inevitability. Inevitability becomes its own marketing engine. Windows had virtually no security architecture by design for so many years, even long after its costly effects became obvious globally, but because it was ubiquitous, thought to be irreplaceable and thus inevitable, it has continued to net Microsoft billions year after year. Likewise, MS Word could get away with some of the most insane formatting problems ever invented by man only because it has so dominated “desktop productivity apps” that it’s become inevitable. If anyone, even Microsoft, were to design a modern word processor today, it sure wouldn’t be Word. And yet everyone else designing a better Word has had a very difficult time of competing with the inevitable. Inevitability is the Kerberos of profitability.
Like Microsoft, Google doesn’t sell best-of-class user experiences to paying customers. It sells their eyeballs to advertisers. The more eyeballs, the better. The most, the best. If it can dominate a market and thus make its products and platforms inevitable, it wouldn’t even have to care about user experience at all.