when your savings increase in value, through no effort of your own and with zero risk, yes, they will sit on them.

Really now? They'll never find a better deal than 20% increase in purchasing power? If this were so, which is ridiculous already, then productivity would cease growing so fast, which means that bitcoin purchasing power would increase slower, which means that opportunities that yield the same as bitcoin had previously been returning, individually assessed and risk adjusted, would become more highly valued and would get funding, so the system is self regulating. It simply selects for investments that clear a decently high bar, like, oh say, using Bitcoin as money and not losing money. I know, SUCH a high bar, almost no investment would ever happen. Psh.