If flying in F meant paying F as in the fare basis "F" as it once did, that type of spend easily supported the sort of lounges which people remember and compare to today. But, that isn't the case anymore. Something has to make up for it and selling "placement" is an easy way to make up for that without either cutting lounge access, raising the bar or doing something else people won't like much.
Indeed, this is a demographic which the marketing folks drool over and while the people here claim that it doesn't work on them, the marketing people say that the facts show otherwise and that this is money well spent by them.