bender
What time is it?
Under the current cut structure they would still get 88% for any game sold via their app, so it would more be a case of "why not".
The bigger question to ask is why would Xbox open themselves up to a scenario where they stand to lose so much more, and could end up seeing absolutely no revenue for purchased/owned games if people simply purchase and redeem Steam keys from 3rd party sites.
The Game Pass gambit....which, to be fair, has certainly been center stage for their marketing team for the last few years. I don't think it's a sound strategy, but it's not like their is a future in the Xbox brand anyway.