The mess exists because the tax code as it stands is absurd. Unrealised losses and unrealised gains aren't symmetric; if you have an unrealised gain then you haven't seen a penny of the money and quite possibly never will so it makes sense not to pay tax on them, but unrealised losses mean you're actually out real money. (Then again, it's not the only messed-up part of the tax code in the US; the handling of stock options from jobs is insane and designed to deliberately overvalue them, meaning that people can end up paying more in tax on them than they could ever have actually made from them.)