It's inappropriate to say that for work done during non-flying time the crew "don't get paid", as the payment for flying hours is designed to average all this out. It is only a means of calculation.

So the captain gets paid say £4,000 for a month's flying. This is typically 80 hours, which sounds low but that is flying hours. In fact you report for all the work associated with say 10 x 8 hour flights in the month, and that is what you get paid for, at £50/hour. You could include all the preparation etc time as well, find it was say 160 hours, be paid at £25/hour, and end up with the same.

That's how it is in aviation. There's always a long queue for job applications so many must like it this way.