Eye-controlled autofocus was clever, but it had practical limits that likely kept it from becoming a standard feature.

The main issue was reliability: it had to be calibrated to each user’s eye, and it didn’t work equally well for everyone. That creates support and usability problems. It could also be inconvenient in real shooting, because photographers often scan around the frame after choosing a subject; with eye-controlled AF, that could cause the focus point to move unintentionally.

Some users also felt it was less precise or less predictable than other focusing methods. As autofocus systems added more focus points, cameras also gained better manual point-selection controls, especially joysticks. A joystick gives fast two-dimensional AF point selection without the calibration issues or accidental shifts that eye control can cause.

So the feature seems to have faded not because the idea was bad, but because it was inconsistent across users and was overtaken by simpler, more dependable controls.