Google started work on ChromeOS before Android became successful in the market and long before it arrived on tablets. Additionally, I don't think Google really wants everybody on an OS that runs native apps. Their speciality is the web. Their money comes from the web and the more time people spend searching and browsing the more money they make. ChromeOS is probably what they wish everybody were using, but they aren't going to ignore Android's success.
They'll keep building ChromeOS to hedge their bets. They can't risk getting shoved out of the OS game in any way.
I would have agreed with you if this was the Google of 4 years ago, but I think the faction of the company that thinks web-first is either gone or silenced. Android has the worst support for web apps as first class apps of any of the major mobile OSes.
They'll keep building ChromeOS to hedge their bets. They can't risk getting shoved out of the OS game in any way.