The main return is the points on the CC used. 2MR points per $ when the surcharge is tax deductible is the main game here and for those of us that like Krisflyer that works and is still a reasonable way to buy points. The extra QFF points is just a small bonus.
Naturally like most of us I prefer "free" points, though in truth all points cost something even if it is just time.
For several decades to fly my family of 5 on mainly annual international holidays (initially in Y, but for over a decade now in J/F) I have mainly have not bought points (whether that be through higher surcharges, high cards fees not offset by other benefits, LifeMiles et etc),
but with retirement now only 3 -ish years away I am becoming less fussy as my ability to gain "free" points will drop off markedly once I do. So I am now also chasing "cheap" points to help build up my various Points Warehouses for my post-retirement phase when I might also shock-horror actually have to start buying long-haul international flights
which is something I have rarely done over the last two decades.
Hopefully I can have enough of a stash to stretch out the much fewer points I will be gaining then. Also my 3 daughters may have to fend for themselves after I retire