I'd suggest a 4th reason: Google has so much money and so many high-traffic properties that it can keep a poorly designed or unpolished product going for years,

I'd suggest a 4th reason: Google has so much money and so many high-traffic properties that it can keep a poorly designed or unpolished product going for years, more than long enough for the original people who designed and built it to move on/up inside the company. Google will just push the product on the front page of some existing property to bump traffic, or get creators/developers to use it in hopes of boosting their existing search rankings, or give away the product for free. Every company would try to do these things but Google has a big advantage. This allows Google to be lazy about product-market fit and avoid asking the hard questions like "is this thing really better than the alternative" and "what's the ROI for people who adopt this". I worked on what I'd consider a failed product, and there was no explicit acknowledgement of that fact ever, we just waited 3 years and quietly turned it off. A more drawn-out version of the same thing happened with Google Plus. There was never anything like a "product postmortem".