Normal social legislation, particularly that without any time limits, although often based on inadequate and suspect knowledge, manages to persist regardless of its success or failure. This is partly because, once instituted, it gathers to itself many forms of vested interest opposed to its reversal, but also because it places the burden of proof of ineffectiveness on its opponents - usually under conditions which makes it virtually impossible to do so.
Bad law is more likely to be supplemented than repealed.