Even if buying goods with crypto is out of the question for you (say, because you don’t want it linked to any physical address), you can still buy a decent range of services. A whole suite of digital services (VPS, VPN, bulk data backup, domain registration, etc) is buyable with cryptocurrencies. A number of places will also accept donations in Bitcoin. Depending on your social ties, you might commission digital art with Bitcoin.

Now, most people I know who hold Bitcoin are motivated primarily by other reasons. But still, I can cut down my cash spending/donations by a few $1000/yr just by doing those things above — which have fairly loose ties to my physical person — with Bitcoin.

With meatspace money. In my case, savings. But I could also have income.

The point is that my online anonymous coward personas and my meatspace identity are as isolated as I can manage.

> With meatspace money

i.e., you cannot fulfil your meatspace needs using cryptocurrency as of yet. It doesn't matter that you are able to isolate your identity online from your meatspace identity.

And this is what gov't can easily enforce - through money laundering laws. If ever cryptocurrency becomes prevalent enough to offer meatspace usage directly, you can bet your bottom dollar that gov't will regulate, and prevent anonymous spending (at least, for any large-ish amounts).

That's true. But still, cryptocurrencies could arguably remain useful, even if they never widely displaced meatspace money. I mean, consider how thoroughly online dark marketplaces have displaced meatspace drug dealers. And perhaps there are other suitable niches.

For example, cryptocurrencies could displace cash for gig economy tips. Maybe they already have, for all I know. Also for online porn and gambling.