cash, or something equivalent to it, allows for the distribution of enforcement of a certain level of truthfulness. Eg, lie about outputs, and can't deliver? Your organization doesn't get paid, and if it keeps that up, too much, too long, then it goes under. In the meantime it's incentivized to find out who caused the lie(s) and remove them from the system.
This sort of thing might work in the right socialist system, but not most of them.