Most people when starting out are, or at least should be, very uneasy about putting money into things with no underlying value or feasible purpose beyond being bought by a greater fool in the future.
I’ve rarely heard it suggested as an investment, but it can actually be realisticly used to goods and services outside of itself and as such does have an actual purpose, which is more than can be said for any crypto currency.
Cash is inflationary, “by definition” as per current monetary theories, meaning it is designed to lose value over time. Not much of an investment.
Also, I can’t use USD, GBP or AUD for “goods and services outside of itself”… unless I exchange them for EUR first, same as any Crypto.