It's not whether they are useful for you, it's whether they are useful for anybody at all. If they did never and will never pay a dividend or have a buyback, then yes, they are a pyramid.
But it was just a matter of thinking a bit about it. Everybody knows what Bitcoin is useful for: cyber-extortion and evading capital restrictions. There are even good reasons for practicing the last one... With that in mind, BTC still behaves like a bubble, but proving it's actually one depends on a quite laborious process of comparing the volumes and estimating how they will evolve.