> Employers can simply say : "this ticket is three hours of work and that is all that we will pay", and your choice will be take it or leave it

In a way, a more empowering choice than being simply ordered to do something impossible.

Employees can simply say: "Dear boss, I bet it will be more like ten hours of work, but if you stand by your estimate you can do it yourself or spend some time looking for an optimist".

If the clock is ticking, estimates aren't going to be very aggressive; when no competent person accepts tickets nothing gets done.