This generalization will have many exceptions, but my sense from past discussions on FT is that the majority of frequent flyers collect miles mostly for upgrades, and the majority of infrequent flyers collect miles mostly for free travel.

If so (and UA's marketing department must know), and if UA is serious about wanting to lure back full-Y passengers, would it make sense for UA to limit mileage upgrades (not free tickets) on international flights to P, PE, and 1K members, and reduce a little bit the competition for the C seats?