It's not that preservation is bad, it's that it's rarely subject to any rational cost-benefit analysis. If the EPA promulgates a new regulation, the resulting flood of litigation forces intense scrutiny of the costs and benefits. But nobody has a concentrated interest to stand up to preservationists. An individual developer might oppose it, but existing land-owners as a whole benefit both from the slimmest of historical significance and from keeping down the total supply of office space, housing, etc. So you don't see cities buried in lawsuits over trying to promulgate those sorts of ordinances.
