Yeah but it was always just an add on, and it's hard to design games for an accessory that maybe 10% of players will have - it's just not worth the effort. If you know that 100% of your userbase will own something, then it can become the core of your experience and design.

In similar vein, Microsoft killed Kinect when they announced that it will no longer be bundled with the Xbox One - suddenly it went from a "must" in terms of integration, to an optional feature that was nearly always cut from any project, since you couldn't guarantee the player would even have it.