All the Volunteer Cabin Crew see, are a minority of crew that will not (refuse to) see, the need to change to allow BA to become competitive again. Every other work group in the company has, without demanding 'no change and a guaranteed future earnings' ad infinitum.
It looks like BA failed to meet that last demand by imposing a bonus.
I wonder how many millions BA would save by guaranteeing current rates of pay? i.e. no more bonuses or pay rises.