Light exercise can certainly be enjoyable. "Nearly as quick" certainly doesn't apply to all situations, If you're doing long distances on the highway where you'

Light exercise can certainly be enjoyable. "Nearly as quick" certainly doesn't apply to all situations, If you're doing long distances on the highway where you're averaging 60mph, then its definitely not an ideal use-case for a bicycle. But if you're driving in the city during rush hour, you might realistically be averaging closer to 10mph. For an example, my morning commute in Shanghai takes about 30 minutes by bicycle, 35 by car, or 40 by subway. Traffic lanes are congested, bicycle lanes aren't. As to riding without dedicated lanes, I can't really speak to that. We have enough bike lanes here that I usually avoid roads without them, but it seems like it would be bad for both cyclists and drivers.