The notes and coins for the euro were first issued in 2002, and the first bitcoin was mined in 2009. What makes one a pyramid scheme and the other not?
The answer surely can't be "every currency issued by a government is stable forever and every crypto-currency will collapse before 5 years".
What I'm saying is, there are a lot of currencies out there, and some are more stable and have a better track record than others. You may not trust yourself to pick a winner among the losers, but I suspect you do use at least one currency from time to time, so you have picked one by default.
The answer surely can't be "every currency issued by a government is stable forever and every crypto-currency will collapse before 5 years".
What I'm saying is, there are a lot of currencies out there, and some are more stable and have a better track record than others. You may not trust yourself to pick a winner among the losers, but I suspect you do use at least one currency from time to time, so you have picked one by default.