> Nobody lives in those downtown areas anymore.

People absolutely do live downtown. Indeed, one of the biggest trends in housing is people moving back in to downtowns.

> It doesn't make sense to make a walking mall in an area where few people will live in walking distance.

So why all the zoning regulations to forbid it? Markets generally won't build where it doesn't make sense. So let them do their job.

> "big fast busy roads"

You can't build your way out of congestion: http://www.citylab.com/commute/2015/11/californias-dot-admit...

People are moving back into a few select downtowns that are being rapidly gentrified. They are not a typical case.

As for the zoning question, it's probably the result of busybody town governments trying to control every aspect of the city lest some developer ruin their perfect vision of the city. I can guarantee that if you propose to build a big shopping complex in the middle of the city you will have people out to protest for all kinds of reasons. They will protest because it will raise their land values (and taxes) too much and force them to move. They will protest because it will bring in people and ruin their "quiet" neighborhood. They will protest because it will affect local water prices. This is how a lot of regulation gets started, because someone is trying to prevent something from happening to their backyard.

> This is how a lot of regulation gets started, because someone is trying to prevent something from happening to their backyard.

There are legitimate complaints, I think - no one wants a pig offal disposal site next door in their residential neighborhood. But we've gone way overboard in letting zoning dictate what can go where.

> They are not a typical case.

But they absolutely are on YC's radar, because San Fran and the bay area in general are ground zero for the housing crisis in those kinds of desirable places.

You could always have Japanese style zoning. To simplify a lot, you can build houses in residential zones, you can build stores or houses in commercial zones, and you can build factories, stores, or houses in industrial zones. So people who want peace and quite have a place for it and nobody is allowed to surprise you with a pig offal disposal site next door. But if people really want to build houses in an industrial zone they can.

People will definitely still complain about that factory. People move into houses directly under the approach path for an airport then try to get the airport shut down because of the noise. People will move in next to a sewage treatment plant and then complain about the smell.