Second Life was an attempt to do a full simulation of life online, a clumsy transfer of what it is to be alive directly from reality to internet; as it turns out, the technology of the internet is good at a lot of the fun parts of Second Life (talking to friends, meeting new people) but those can be performed by new systems, unburdened from trying to be a simulation of something else (messageboards, forums, and so on to Facebook/tumblr/twitter etc). The other parts (from raising virtual pet rabbits to the whole concept of walking from place to place) were just sort of fluff, and so the experience faded not because it was a bad idea, but because it could be done better once it stopped caring about the simulated fluff.
Cryptocurrencies may not be that useful, but there's a possibility that they prefigure something larger; they're still mimicking a pre-existing model of currency, economy, and exchange that can itself be disrupted. If we analogize cryptocurrencies to Second Life, it means they'll fade because their functions will be replaced by a completely new way of interacting/handling value, and the blockchain can still be an important technology for that. (For the record, I think it's too soon to tell, and am not that optimistic about any current blockchain ventures.)
If you think cryptocurrencies have no utility at this point, you have your head in the sand. To use money electronically right now, you need a bank, you can't do it yourself.
Another alternative would be to trade goods or altcoins for fractional BTC.
https://www.reuters.com/article/us-fidelity-bitcoin-idUSKBN1...