People don't use cryptocurrency "in exchange for goods" to any significant extent. Major merchant adoption of Bitcoin peaked years ago. And at least in my area, the same goes for local merchants; Bitcoin here is extinct.

Bitcoin is doing what, 100m transactions per year? Most of which are not for physical goods. Venmo, which started around the same time, does over 2 billion. M-Pesa, a "digital money" solution the same age does 15 billion. US credit transactions? 45 billion. Debit? 75 billion per year. And unlike Bitcoin, most of those are what people would call real transactions. Bitcoin's real use is a rounding error.

Cryptocurrency can be here to stay and also be driven by scams. Set up a Google News alert for "Ponzi scheme". Ponzi was active 100 years ago, but his approach is more popular than ever. As they say, there's a sucker born every minute.