Sometimes a Mapillary track could be the first time a road or path is being mapped. So it could be required to only snap if within certain distance.
Additionally, not all sequences are taken from the road, but on the sidewalk. If these are mapped on openstreetmap, it’s not easy to tell if it should snap to the road, or the sidewalk.
I think that some of the image processing, that mapillary does, actually figures out that where photos are taken in a scene, as various viewports. I wish they’d use that data to tidy up areas with numerous sequences. And more sequences in an area will improve this! Which would encourage more coverage.