The instructor is working in just the same way as say a plumber in your house is working. The student I very much hope is working towards the attainment of a PPL which for many is the first step towards a CPL or they are a professional student training for a professional licence CPL ATPL and all the necessary additional ratings night IR etc.
As an ex crab you may have had everything paid for by the Queen and experienced the luxury of being paid to learn to fly. But in the commercial world the student pays for everything makes great sacrifices. Their training continuity is vital to their progress and their bank balance.
Tube passengers are not working when sat on the tube train but the driver is paid and allowed to go to work.