https://www.techradar.com/news/xbox-live-gold-free-games

One of the main benefits of being an Xbox Live Gold subscriber is definitely the fact that each month you get access to a range of free games across the Xbox One and Xbox 360 platforms. If you’re an Xbox One owner, backwards compatibility means you get to take advantage of the Xbox 360 titles too.

This is a great way to try games you might not otherwise have played, whether because they're indie titles that slip under your radar or simply because you don’t have the funds to buy several games a month.