Because even though Starfield will be sold in physical stores, the "game" you go into the store and buy for PC will not contain a Game Disc. Instead, you simply get a code, which you must subsequently redeem to download the game.
Starfield is for many among the most anticipated games for a long time. It is the first time in many years that Bethesda, the developers of the Elder Scrolls series, is launching a new game world.
However, the release will apparently be completely without the possibility of actually owning the game physically if you want to play on PC. The game will contain a Game Disc in the Xbox version, but even the large Constellation Collectors Edition for PC will not contain the Game Disc, but only a code for the game.
You will probably be able to choose whether you want a code for Steam or for the Windows Store.
Starfield is currently set for release on September 6, 2023.