Flying pay is simply the money you have to pay aircrew to recognise their skills, and to recognise the money that they could be paid elsewhere.
So - a retention bonus then. If someone isn't being retained (PVR) then why pay them money to recognise they have transferable skills? We've not retained them, so we have the current (correct) system.
I can see you also think everyone not in a cockpit wants to be in a cockpit.
[insert ironic smiley here]