I wish people would stop referring to this as Microsoft trying to compete with steam, and suggesting this somehow represents competition that will benefit consumers.
This is Microsoft specifically not putting a game on Steam or other storefronts so that they do not have to compete with them.
They are within their rights to do so, but this is an anticompetitive move.
If their aim was to promote healthy competition, they would make the game available on a variety of storefronts, and allow customers to use whichever they preferred (for a variety of reasons such as pricing, user experience, customer service and features). That is not their aim.
I'd prefer if it was on a variety of services, but Microsoft decided otherwise.