The problem is not that those missing or forgotten formats won't have a good number of listeners. The issue is the advertisers. AM-1290 [WJBR] played Standards and had pretty solid ratings for a 1K AM station, but they weren't making any money. Advertisers want young, not older listeners. Today AM-1290 is WWTX [Fox Sports Radio]. The ratings are far less, but they have plenty of spots, because the audience who mostly listen are young men. That's business, its all about the money.
So, as an older listener [age 64] to hear the music I want I go online to I heart radio and make a station that plays the music I want to hear [I've made a number of music stations for myself there - one plays Baroque Music, one Mellow Piano music, another Big Band, another Jazz Piano, 60's oldies, one 70's pre-disco oldies]. So I don't listen to OTA radio for music any longer.
I can also find old time radio dramas that I enjoy hearing, online. I'm not sure how these online services make money, but I sure enjoy hearing the music I personally like and enjoying the Theatre of the Mind experience in hearing radio dramas [ a very different experience from watching TV dramas]. Don't get me wrong, I do enjoy watching TV shows too, but also enjoy old time radio.
I listen to OTA radio, both AM and FM: for News, News/Talk [WDEL-AM/FM, WILM-AM, WHYY-FM]; Sports, Sports/Talk[WDEL-AM/FM, WWTX-AM, WIP-FM, WPEN-FM]; NPR programming [WHYY-FM, WDDE-FM-Dover]; Jazz and Classical Music [WRTI 107.7-Wilmington's translator from Philly 90.1]. Otherwise I listen online. I'd listen to music on OTA radio if they played what I want to hear, and there are plenty of us BabyBoomers who would, but the advertisers don't want us to reach us, they want the younger audience thus what gets played on OTA radio. It's purely business.