https://phys.org/news/2018-08-microsoft-monthly-xbox-subscription-fee.html

The subscription plan, which is unique to Microsoft and has been rumored for some time, offers a lower barrier to buy gaming consoles, which carry somewhat hefty price tags.

It's also a way for Microsoft to get gamers to sign on for its online gaming services, which encourage two growing trends in gaming—streaming games, rather than buying them, and playing with others online.