I always knew night riding felt weird, but I only realized last night what really caused the visual effect.
With little or no visual horizon reference and not much peripheral vision, the rider focuses almost exclusively on the patch of light on the road ahead. Things are visible in the patch for a much shorter time than they would be in full light, so the mind barely registers them compared to the seemingly unmoving patch of light itself.
Other senses convey a sense of motion and speed, which only highlights the fact that the most visible object in front of you never gets any closer. The patch becomes an object in its own right.
Off-road, larger objects come through the light to provide a bit more visual reference to speed, but even then the confinement of the light patch alters perception.
In cities, with more ambient light, the effect may hardly seem noticeable. Out here in the country it's almost constant.