> Are cryptocurrencies supposed to be a potential replacement for real life cash?

I think the better word would be alternative, rather than replacement.

Crypto currencies have way too many flaws to be really useful as currencies.

Not just usability, technology, fees, etc, but the very deflationary nature of most of them makes them unsuitable as a currency because the incentive is hoarding, not spending.

But...you can still use them as a mean of transferring money. So they are absolutely an alternative.