Then shouldn't every deflationary alt-coin also be valued like gold? You can see where this is going...
The network effect should not be underestimated. The world is filled with examples of inferior systems that exist simply because they have more momentum than others. Investors demand a “store of value” investment vehicle. Up until now, gold has led that role. Now Bitcoin will take over. Not because it is the best, but because it is first to market and has enough momentum and utility to replace it.
Gold is a weirdly sticky anachronism of a wealth store that never made any sense in the first place.
Thus making tokens out them meant said tokens would last generations, and withstand the rigors of international transport.
As best i recall, gold and silver were rarely popular for domestic trade. There more common materials were used. They were instead used for international trade.
In the end people have come to confuse the token, a way to do trade accounting without an accountant always present, with the metal it was made of.