Maybe the cyclists don’t like the stop signs that the path frustratingly has but the road does not? Around that stop there are two within a few hundred metres, and frequently stopping (or slowing down fot a rolling stop) makes riding slower and more tiring. That’s probably not nearly the entire motivation, though.
Air quality can certainly be impacted by density, but neighbourhoods that aren’t car dependent promote exercise by giving people the ability to lak or bike wehn going out instead of driving (which can also help the overall air quality).