I dont think the goal is to increase cash value, I believe the goal is to reduce the overall liability they are carrying on these miles. The more opportunities they give people to cash in their miles the more likely people are to spend them, and the less that are sitting on the books.
If you look just at FT that is a brilliant strategy. Many of us travel so much for work that using miles to buy airline tickets just doesnt happen, so we sit on millions (yes some purposely save them, but for me personally I just dont have a reason to use mine I am already flying so much). But given the right other opportunity to use them I am more likely to.
This also will benefit where husband travels for work all the time and doesnt care about miles, wife can use those miles for non-flight purchases.
It's a smart strategy