> Binocular vision ought to be good enough for a vacuum.

It could be, but it just is not. VSLAM robots were practically significant worse. There are a lot of limitations to multi-ocular vision for a robot vacuum, for example the relatively featureless walls and few features across the horizontal binocular axis.

Neato was never as big as iRobot. They didn't fail from commanding heights, they never were that successful to begin with, for entirely different reasons. If they had managed to get to iRobot's level of ubiquity and distribution they would have had a much better shot of still being around nowadays.