"but they could (in theory at least)", uhm, what theory is this? No seriously I would like to hear the theoretical basis for this assertion (though I think you are totally wrong as well).
The simple fact that people like GP exist, and that there have been enough of them to propel the market cap of BTC et al. to billions, suggests that people like GP will continue to exist if the economy crashes.
In fact, if the economy were to crash, it would only take a handful of high volume BTC purchases, I'd bet, to cause another spike in price as people see an opportunity to shelter their finances.
Yes, it is high risk, but you're not just throwing away your money. BTC is much like gold in this manner - to the lay person, there is little value in the commodities other than as a store of value, which becomes more and more appealing as price continues to rise. Look at gold. Markets do not always appear to be rational.