I think a lot of the miles are used for upgrades, Y to C. On Transatlantic UA lately, I think the majority of the people in C with me are UG.
The Airlines may be considering clearing C out for Revenue Passengers, then cutting the C fare from the typical US origin rt $7,000 to the typical Europe origin of $3500.
Perhaps airlines are being forced to think in terms of cost effectiveness. If you fly out of IAD, DEN, ORD, SFO, you have to do UA. Atlanta,DL, DFW, AA, and so forth.
Everyone talks about Southwest and their generous program, but few fly on Southwest, because they don't go anywhere to speak of.