I'd encourage everyone to guesstimate how much distance could be taken out of their commute or drive to the city by removing parking lots, huge highways and tens-of-foodball-fields interchanges, large set-backs and front lawns to keep people away from unpleasant roads, and so on, then check whether they could bike that distance in what it takes to drive.

When I encountered the idea that cars being common causes them to lose all benefit for most people while also causing them to become necessary, I initially thought it overblown. Then I ran the numbers. Well. Crap.

[EDIT] and don't forget to factor in minutes or hours per day spent working to pay for car+maintenance+gas.