If you're saying the pilots aren't paid for time they're working but not flying, I think that violates some labor laws.
We are under the Railway Labor Act. In many ways, it differs significantly from the labor law under which most Americans work. Sometimes that's good for us, often it isn't.
I leave for a trip tomorrow. Will leave the house about about 5pm tomorrow to commute to my domicile. I'll pay $104.49 for a hotel room. My trip starts Wednesday morning 08:33. At that time, I start earning $2.45 per hour per diem. That will continue until 15 minutes after the arrival of my last leg on Saturday.
At 09:33, I'm scheduled to depart for my first destination. When the brakes are released for pushback, my pay-time starts. It's scheduled to be 2h03 of block time, arriving 12:36. When the brakes are set at the gate my pay stops. I'm then off to the hotel until the following morning after 3h18 on-duty and total pay for that day is the 2h03.
Day two is 8h37 duty and 6h41 flight time/pay.
Day three is 8h57 duty; 6h48 pay.
Day four is 8h49 duty; 6h32 pay. Finish in Chicago at 13:19 and hope I can get on the first flight home which would get me home around 16:45.
I leave home Tuesday around 5:00pm, arrive back Saturday around 4:45pm. I fly 7 legs and am paid 22h04 plus about $188 per diem; $104.49 of which I'll spend on that hotel room the night before the trip starts. That'll leave about $84 for meals. I'll buy six or seven meals on the trip.
Overall, a better than average trip. Only one short (<12hr) layover and no more than two legs in a day. Many of 4-day trips pay only 20h00 and fly more legs (i.e. more work & duty that you aren't being paid for).