Chrome is in a monopol position. If they decide to ship a new feature .. then all the other browsers need to implement it as well, or their users assume their browser is broken.
Okay but that's still not the same as enforcing a standard, in any way... You're suggesting the W3C should simply roll a "reference browser" that supplants Chrome so they can force standards on users themselves. That really doesn't seem like a great way to do it.