The human system is so good at providing a stable percept of the world that we have no intuitive appreciation of the physical constraints under which it operates.
Humans have foveate vision.
This means that to see an object clearly, humans must move their eyes such that the image of the object falls on the fovea. Human eye movement is not smooth. It is composed of many quick jumps, called saccades, which rapidly re-orient the eye to project a different part of the visual scene onto the fovea. After a saccade, there is typically a period of fixation, during which the eyes are relatively stable. They are by no means stationary, and continue to engage in corrective micro-saccades and other small movements.