It’s also primarily a niche pseudo currency that’s arguably more regularly used for crime than legitimate purchases.
That’s true for cash as well, but that’s because of a few factors:
credit cards are more attractive due to rewards
sales tax makes buying things w/ cash a pain in person
you can’t use cash online, the closest you have are debit cards, but breaches make that unsafe
Cryptocurrencies can solve these problems. Since it’s digital, there’s nothing physical to carry around, online purchases are secure, and some vendors charge a lower fee for accepting crypto (e.g. based.win has a 10% discount for Monero). Since it’s distributed, you’re not stuck w/ 3-4 “networks” to process transactions, so transaction fees are generally lower (e.g. Visa/Mastercard/etc generally charge ~3%, whereas Monero charges a few pennies, regardless of transaction amount).
The reason it’s more often used for crime is because few vendors accept cryptocurrency as payment, mostly because demand is low. The more people that use cryptocurrencies for legitimate purchases, the more companies will accept it and the ratio between legitimate vs criminal transactions will go down.
I wouldn’t be surprised if cash is more often used for crime than legitimate purchases, mostly because cash is annoying to use. That doesn’t mean we should eliminate cash, it means we should make using it less annoying (e.g. include sales tax on listed price and not just calculated at checkout). I see cash used a lot more in states w/ no sales tax, and I hear Europeans use cash a lot more as well because VAT is included in the list price.