Being in a full bike kit doesn't mean someone is playing Tour de France. For people (like me) whose quotidian bike commute is 10+ miles each, it is incredibly uncomfortable to wear street clothes, and it's very inconvenient to ride several 5+ miles out of the way to take an isolated path. Besides which, the impossibly small portion of infrastructure that doesn't allow car traffic often requires cyclists and pedestrians to mix on narrow paths that are poorly maintained.