Tech bros move into cities like san fran where it's impossible to find housing at a reasonable price. Since they moved in they don't have the incentive of someone like a landlord to prevent other people from building houses, all they care about it getting themselves cheaper housing. When they eventually make enough to buy property somewhere or become a small landlord they will change their tune and become advocates of "historical preservation" and act to keep their property values and rental income going up as much as possible.