It's more than that. Money's value depends on everyone's collective attachment to it.
The winners of a game remain so, only as long as a significant number of people are playing.
Ditto with USD, ditto with BTC.
UBI is one way to keep people playing; but I'm extremely wary of this idea. UBI without some sort of communal/anarchist/kibbutz-ian distributed structure binds society in yet another way.
'You're free as long as you do what I want', is not something we as a society should want, yet it is almost universally true. The US wants nations to be 'free' so that they do what it wants; it's only natural that this extends all the way down to the individual.