Why are Cryptos called currency?

As a curious observer of the financial world, I often find myself wondering: why are cryptocurrencies colloquially referred to as 'currency'? After all, the term 'currency' typically denotes a form of money that is issued and regulated by a central authority, such as a government or central bank. Cryptocurrencies, on the other hand, are decentralized digital assets that rely on blockchain technology for security and verification. Despite lacking the backing of traditional financial institutions, they have gained immense popularity and are often used as a means of exchange. So, what is the rationale behind calling them 'currency'? Is it merely a nod to their functional similarities to traditional currencies, or is there a deeper connection that justifies this terminology?