Advocate for isn't the same as doing.
In practice, the "get rid of cars" part happens (because it's free), and bike lanes get drawn (because it's effectively free to paint lines). But the transit never gets built (because that would cost money). The net amount of transit capacity drops in most of these changes, even as most cities are experiencing population growth.
For example, this article mentions building superblocks in NYC, while neglecting to mention that NYC subway system has been over capacity for over a year - http://www.wsj.com/articles/new-yorks-subway-system-cant-kee... Superblocks in NYC would literally eliminate transit capacity and replace it with nothing. It's net destruction to capacity. It's suburbanizing an urban environment.
> Traveling by foot is a form of transportation!
I love to walk too, but if walking were a viable option, the cars wouldn't exist in the first place. This isn't some American stripmall being discussed -- Both NYC and Barcelona are already quite dense, and some of the most walkable cities on Earth. If more walking were possible, it would already occur.
And yet, some people are still driving cars there, even though it's already extremely inconvenient to do so. We should be studying why it's occurring, and offering up legitimate alternatives that are better than the current solution.
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It's a common new urbanist trope, to read some Jane Jacobs and then blame cars for every problem in the entire universe. But cars aren't some evil villain -- they simply represent a person, who needed to go to a place, in a reasonable amount of time.
The best way to eliminate cars is not to punish that person who just wanted to get somewhere efficiently -- they've done no wrong. The best way to reduce cars is to provide better (cheaper, faster, easier, safer) ways to get places that don't require cars, let people voluntarily choose these better options.
New urbanists are great at talking about that. But they're not great at actually doing that. They'd (usually) rather hit people with sticks, than offer up carrots. Which is a shame.