Even comparing full Y to full C and full F, the numbers are still skewed, although perhaps to a lesser extent.
So there must be something else going on.
Who would participate in a mileage programme with an oneway u/g for 100 K miles a C award for 240 K miles? It is just a matter-of-fact calculation: you have to give away
x perks to bind a group of
y customers to your product.
But SHHHH again, it
is a bargain.