There's a huge difference being "commonly used for" and "is a". The vast majority of emails and phone calls are spam. But it would be naive to call either of them - particularly email - fundamentally spam services.

Just because people leverage the hype & mostly unregulated nature of most crypto, doesn't make it innately a ponzi scheme. Yes it's a mess. Yes it needs better regulation. Yes, a large number of "use-cases" are better served by existing solutions.

But this is mostly because we're still very early in a slow-burning hype-cycle. There are some fundamentally unique services supplied by (some) currencies, like Ethereum smart contracts (e.g. de-centralized escrow), that enable fundamentally new and useful interactions. It is precisely these features which give (some) currencies innate value beyond speculation. I personally plan on waiting for the hype cycle to shake out a bit longer before I get too involved.