The question I have is, why do remote towns and villages, some in middle backwoods America, have full time AM and FM translators playing classic oldies and country from the 50's and 60's, some so obscure they were only played when first came out.. The audience they are reachng doesn't know the difference between Frankie Avalon, Anette or Fabian from Sam Smith lol. Why doesn't the big cities on the east coast where the residence grew up on this music, know every word of every song and embraced it not have a local outlet for it. Makes no sense, but signals like WFAT, WKCE, KFXM and many, many, others, some in one horse towns are playing this and all the floundering AM's in NYC and Philly won't budge.
Those super-oldies stations that succeed are in smallish markets where there is practically no agency business. They sell to local advertisers who evaluate media based on service and the cash register and don't use ratings books to buy.
The larger the market, the more agency business there is. Agencies place ad buys according to their client's marketing department's specifications, generally meaning that they don't ever target folks over 55. So, in a major market, you won't see major stations programming 50's and 60's and even earlier 70's.
The secondary answer is that many of those little town stations just don't know any better and there is limited competition to prove how wrong they are when they play some of those amply forgotten songs. The owners think that is "variety" while listeners think it's just "songs I don't like". But they don't have ratings and they generally don't have good programming skills. Occasionally it works in the WLNG fashion, but generally it's just bad radio.