I find the shortage of drivers to be very surprising.
I was under the impression that "everyone wants to be a train driver" on a heritage line, and that the real challenge was recruiting sufficient volunteers for roles perceived as less glamorous, including P-way maintenance, grounds and premises maintenance, station staff, and similar roles.
I think everyone wants to drive a quad bike, except those who have to. I'm sure the glamour and excitement of driving a steam train doesn't last in the long term for everybody.