A kid with training wheels is like a brand-new student driver: they need to practice somewhere where there's no traffic until they can handle their vehicle; then and only then are they ready to join the flow of traffic.
Kids with training wheels are mostly not really going anywhere. When you see them on bike paths, they might venture a quarter mile from the trailhead, but that's about it -- then it's turn around and back to the car. They're in practice mode, is all.