Valve tried trackballs with the Steam Controller but ditched them for trackpads that emulate trackball physics. They found small ones felt bad but big ones were too bulky and heavy. Clearly they like that idea, since every controller-like thing they’ve designed since includes pads.
In a stationary device like a desktop trackball or an arcade cabinet, they settle but a handheld device is moving very slightly while being held and more vigorously when picked up/put down, which can move the ball. Trackpads won’t do that.
Valve tried trackballs with the Steam Controller but ditched them for trackpads that emulate trackball physics. They found small ones felt bad but big ones were too bulky and heavy. Clearly they like that idea, since every controller-like thing they’ve designed since includes pads.
Also they can spin on their own in a handheld-
In a stationary device like a desktop trackball or an arcade cabinet, they settle but a handheld device is moving very slightly while being held and more vigorously when picked up/put down, which can move the ball. Trackpads won’t do that.