I can pay my non-imaginary taxes with dollars. All my other bills also helpfully accept dollars. This gives dollars a useful non-imaginary quality crypto does not have.
There's a handful of objectively valuable things like air, water, and food which I literally cannot live without. The value of pretty much anything else is imaginary because it's subjective.
The value of cryptocurrency is just far more imaginary than dollars, euros, or even gold.
You can believe that phone bills are a purely imaginary human construct that has no physical meaning and your phone will still stop working when you stop paying them.
At some point these things we conjure up out of our collective imagination are every bit as real as the ground hitting you if you jump off a building.
That counts for crypto as well though. If your phone bill is in crypto, and society believes (!) in crypto, then you might have society enforcing it's beliefs with the full force of the law.
I.e. imaginary.
Your phone bill is just another level of abstraction on top of the USD imagination.
In the middle ages witches were believed to be real by enough people to burn them on the stake. The full power of the state was behind this. Unless there's scientific evidence of sorcery now I think witches are imaginary.