When Apple announced its intentions for gaming on the new Apple TV, the thing that made for the biggest excitement was the usage of MFi controllers. The Siri remote might be okay for general navigation on the system, but it is definitely not the best input for gaming, and it was clear that Apple knew this. That meant that if you wanted to actually build a real game instead of just a casual nonsense game, you could.
Unfortunately, Apple has let the wind out of developers sails with a single clause in the tvOS developer guide:
Your game must support the Apple TV remote. Your game may not require the use of a controller.
That kind of rule might be a good way to ensure inclusion into your game store, but it doesn't encourage developers to build games that really rock. There was little hope that the Apple TV would see hardware sales because of its gaming capabilities at first, but there was some hope for them with full controller capabilities. Unfortunately, no full-scale games can be built to be playable with the equivalent of a single D-Pad and 2 buttons. That kind of input can only support small, casual-style games, and those games cannot sell hardware.
This rule is a change from the initial manual, which stated clearly,
Unlike iOS apps, Apple TV apps can require the user to own a full game controller that supports the extended gamepad profile, but requiring a full game controller is highly discouraged. When you restrict an app, only users who already have a full game controller will see your game.
It is always possible that Apple will reverse course on this decision if enough gamers and developers complain about the limitation, but the company is not known for bowing to customer demand. Maybe this will be the exception to the rule.