I can't say that it doesn't happen. In freight, they're all paid on a mileage-based system. Once you achieve a certain number of miles in a month, then you can book off. It's a pretty high number. It's like 4,000 miles, but once you achieve that, you can book off. So might somebody try to get a couple of days off at the end of the month by not taking a day off in the middle of the month? Yes, but they still have to comply with the work/rest rules the way they are now.
The problem in doing that is that they don't control when they're going to work, so they have to take their call when their call comes. If they stay good at the away-from-home terminal, they're still off for six or seven hours, but then they're right back at it to try to get in to get out again.