One thing I never understood about crypto currencies was wouldn't new crypto currencies just displace them? Even if you could say the supply of bitcoins is limited by algorithms, a new company could easily just make a new currency. Are people still going to value the original bitcoins 20 years from now, with hundreds of alternatives cropping up?
That's the consequence of the regression theorem. There needs to be some underlying value which would make owning specific currency valuable. With gold, the original value is created by non-monetary uses of the gold. With fiat currencies it was initially backing by the gold, and then ability to avoid persecution by the governments (either due to direct prohibition on competing currencies, or due to requirement to pay taxes in specific currency). None of that exists with private fiat currencies having no backing by PMs or government-enforced currencies.