I can think of many reasons why folks would want to use a custom browser built on top of Chromium rather than Chrome. Take Opera for example - Adblock and VPN

I can think of many reasons why folks would want to use a custom browser built on top of Chromium rather than Chrome. Take Opera for example - Adblock and VPN are two services that can live more efficiently deeper in the core versus the extension layer where they are on Chrome. And these are two services that Google does not want to promote any more than they have to in order not to shed users. Browser competition is great for the market, the last thing we want is to end up in an IE6 type situation (and yes it can happen to anybody, even Google).