This is a conglomerate of the tales I have been told where volunteer staffing has increased, and the existing paid staff have suffered with mismanaged hand overs, miscommunication and outright false promises.
Paid staff with years of expertise, experience, stores of knowledge, thousands of pounds of education, seeing their positions packaged into chunks and those chunks handed over to volunteers (some of whom also posses all those qualities, yet can't get paid work) until they are left staffing tills, cleaning, and providing security detail. Paid staff reassuringly told that "we won't be replacing you, you will still have a job!" and slowly finding that their role now only features the tasks that managers can't attract volunteers to.
Yes, many venues need the voluntary help, but it has to be properly, honestly, decently managed.