Could there be a bit of truth in some cases?

For example, a heavily loaded flight has no plane because the plane has mechanical problems or is stuck at some other airport due to weather or missing crew. Then the airline takes a plane from a lightly loaded flight to fly the heavily loaded flight, resulting in the lightly loaded flight being cancelled.

The other thing is, many airlines treat non-elite passengers so poorly that many people think cynically about the airline's motives whenever there is some kind of problem.