It is quite reasonable for it to be proprietary as developed by a small team that still needs to see return on its investment. Last thing they need is someone with a pile of cash and/or reach taking their engine and launching a new browser with it, stealing their thunder.
Monetizing a browser is not easy if you are not in the data-monetization game.
> Monetizing a browser is not easy if you are not in the data-monetization game.
How do we know that they aren't?
It's like free money for a tech company. There's little or no disincentive, and they don't have to do a lot of extra work - the data is already sitting around waiting to be collected.
Monetizing a browser is not easy if you are not in the data-monetization game.