This generally happens when committees are too far away from the actual development. It happens all the time at companies too with non-coding architects too. Standard setting bodies need to understand the pace of modern development, they spend way to long in the discussion phase. Once their is running code a lot of the discussion is basically over, and it's a choice of writing the spec to match what happens or browsers documenting the "quirks" with the standard.

That's not to say chrome isn't busing their market share. Even if there were more players though, it's a matter of Google gets MS/Apple/Mozilla to agree and nothing else really changes.