easy answer:
private license = you pay to fly
commercial = you are paid.
the problem is not only here , but in the responsibility of the CAA. the Airline, and the pilot paying.
what would happen in case of a crash? who is responsible?.
the copilot is paying to fly, he doesn't have the same responsibilities as a "real" copilot as he is still a "student", even with 450 hours on type.
( the guy crash the plane after his line training. He has been released by a instructor captain.The pilot is STILL under training!!! the contract says he bought 500hours of line training. How is that possible??)
he can go away with a : "I pay to fly, not my responsibility, go ask the CAA or my school, they have copy of the contract, I am a student, I pay to fly!!!"...
do passengers know that their pilots pay to fly???