It isn't, it is more difficult, but it is a different kind of difficult. That is why both have a place, and will continue to do so until a social collapse, at which point only gold will remain. But until such a point, bitcoin exists as sometime harder to trade than gold in some ways and easier in others. It also borrows a bit from fiat currency in that it only has value because we agree to give it value (at least greater than the value of as single cut of cloth/plastic paper). Gold has some level of intrinsic value in both how resistant it is to change, its socially desirable look, and its practical use.