Debit or credit card based transactions are backed by the holders ability to assume debt varified early by banks before issueing them. Crypto currency on the other hand has no such backing. Its value is based on the demand and supply of it at the crypto exchanges that handle the crypto currency. . So in fact for buying and selling one don’t use crypto currency directly in many cases except in few agreed transactions. One buy and keep cryptos and its value rise. In future one can convert it back to dollars. Otherwise where ever it is acceptable, one can exchange for products and services using it. When you exchange it one can use the dollars exchanged back for paying your credit card bills or credit it in the bank for debit card payment.