I think you are missing the point if you think the author implies that they are completely banned. They are obviously not all banned. The issue is that they are

I think you are missing the point if you think the author implies that they are completely banned. They are obviously not all banned. The issue is that they are banned in certain places. Most cities strictly regulate where you can build different things and have restrictions on setbacks and parking for all of those things. In my midwestern town, I could not tear my house down and build an apartment. It is zoned for 'single family 2nd density residential.'