We already see how negative interest rates is a threat banking systems in Japan and in Europe it is a dead end.
They won't induce growth, but will divert attention from reforms and as result current economic system will destabilize itself even further.
A diversion, yes that's right. Divert their attention: "Look over there, a squirrel!" And hide their machinations from the masses.
BTC still has a price that is too volatile to serve as a reliable Store of Value now. Perhaps when there are some real losses (real estate or stock market crashes), then BTC will get more attention.
And do not overlook that border-less world of Bitcoin either. Economic Protectionism usually signifies that things are very bad, the boot then comes down... BTC would be a way out.