Work in our city and get a $20,000 federal tax write off...?

California won't allow building a park bench there, much less a new major city.

California is a state. You might be thinking of Marin county, which surrounds only about 12 miles of the 101 freeway, so this is nonsense from multiple angles.

I'll repeat my answer with less sarcasm: Because building new cities there is not legally allowed. It's physically, but not regulatorily possible.

Any large construction needs to go an approval process, the article talks about the same thing. This article is about a giant project, the point isn't about any single place that would be more or less resistant. It is about the fact that large amounts of unused land with close proximity to major cities is common.