You have a good imagination. IE is currently not even challenged.
They should if they get nothing out of it being dominant.
They got EVERYTHING out of it being dominant but that game is over. All a competing browser can be is "just like IE - but better". Game over. Microsoft already obtained what they needed.
The money comes from tools to create and deliver content. MS set the standards for the browser so that battle is over.
A better browser is like buying a third party remote for your TV - you watch the TV for the content, not to use the remote. A neat remote is cool and may make it easier to get to the content you want but your pay for the content.