Should be a nobrainer, but cars has been the status symbol for decades and that makes it hard for people in power (who always are attracted to status and might) to change things. But so many arguments back up more cyclists. Apart from CO2, particle pollution, traffic accidents, health of the drivers, noise pollution etc. there's also a lot less space needed for bicycle traffic.
Here's some footage from Copenhagen and in almost every frame (best seen in the shots from above) there are more people in the bicycle lane than in the car lanes. Most of those cars, especially in the rush hour have only one person inside.
Very true.
That's a neat video. That's a lot of bikes!