Cool, I suppose, but why wasn’t it a feature at launch?

https://games.yahoo.com/news/microsoft-just-stunned-us-announcing-backward-compatibility-xbox-164943390.html

Wooow! No one really expected this, but Microsoft just announced backward compatibility for the Xbox One, meaning Xbox 360 games will finally start working on Microsoft’s latest-generation console.

Microsoft’s E3 press conference is underway and the company kicked things off with a bang. Beginning today, Xbox One owners in the company’s beta program will be able to play any one of more than 100 Xbox 360 titles on the Xbox One.

The new feature will launch for the public this holiday season, but not all previous-gen Xbox 360 games will work; Microsoft will have to add the updated games to its store.

And of course, Xbox One users will only have access to Xbox 360 games they’ve purchased in the past.