Xbox One will get demo's in the future, it's just that Microsoft hasn't quite got around to providing them yet.
Microsoft's Major Nelson revealed that improvements such as demos and an upgraded party system will come 'over time,' following complaints from fans over the current version of the dashboard.
"It is (and always has been) up to game developers to do demos for their own games. [There'll] be more demos for Xbox One as the platform goes forward."
What improvements would you like to see to Xbox One?