The entire concept of fiat currency is abstraction. It requires layers of illusion to maintain its integrity. At it's core, those in charge of the ledger can change where money goes and who has it.
Bitcoin isn't dismissed as "fairy money" because it's digital but because it doesn't have a similar rather large built-in reason to assume there will be a non-trivial demand for it at a particular point in future.
However [purposely] opaque certain other classes of financial asset are, they tend share the general property - which BTC doesn't have - of representing one entity having a future claim on another's resources.
Then why does the US still maintain over 8000 tons of gold at Fort Knox and elsewhere, 45 years after closing the gold window?
Of course even before 1971 paper currency was an abstraction as well - it was a piece of paper to get a commodity, not the commodity itself.
There was approximately $1.48 trillion USD in circulation as of October 20, 2016.
There is about $8.22 in digital assets for every $1 we have in physical gold.