My view is that there is an over-romanticism about the mom & pops.
WABC today is basically a mom & pop, run by the billionaire pop, known as John Catsimatidis.
Yet the OP makes a good point. Because WABC is running local talk shows during most dayparts, outside of its 24-hour simulcaster on Long Island, you're not going to hear those shows over on the air radio anywhere else.
Let's take the analogy a step further. People growing up when I was a little kid back in the late 1960s and early 1970s knew of all these fast food restaurants because we heard their commercials on the radio. But we also knew of places that didn't necessarily advertise on the radio that our parents sometimes took us to when their friends were in town and they wanted to show off. What most of us didn't know back then (though it was very predictable) was that those "show-off" restaurants would be replaced, not necessarily by fast food chains, but by restaurant chains nevertheless. And, for the sake of consistency, the recipes used in each of the national chains' owned or (more likely) franchised restaurants was standardized so that if you visited that restaurant in Phoenix, you would have the same food offerings and quality as you would if you visited that chain restaurant in Atlanta. In other words, no more market differentiation *and* no more reasons to bring your out-of-town friends and relatives to a great restaurant that can be found nowhere near where they live. And, to top all of that off, kids today (I know this because of the behavior of my 14-year-old nephew) are being raised, with the able assistance of television commercials, to believe that the food they are getting at those food places is the best food possible for them.
Now let's step back and look at this from the radio perspective. When I look at the charts of the various top-40 outlets available on the ARSA survey site, I find something funny. I find that while everybody is playing pretty much the biggest hits, there are a flurry of records that do well in one market but not another. The Who's 1966 entry, "My Generation," is a great example of this. While the song got airplay and made radio station charts in Los Angeles, San Diego, San Bernadino, and San Francisco, CA; Detroit, MI; and, according to Larry Neal, KOMA in Oklahoma City, it never was played in New York, Chicago, Cleveland, Pittsburgh, Minneapolis, Omaha, or Milwaukee while it was a current. In other words, people outside of the first set of markets I mentioned never got to hear "My Generation," when it was first issued as a single and the song ended up dying nationally, peaking at #71 on Billboard, if memory serves. And there were other songs just like that that you could hear in one market but not another. Gradually, this went away in the 1970s only to briefly return after the end of disco as a popular force and before the Mike Joseph hot hits format took over in (roughly) 1983.
All of that is gone now. Most top-40 outlets are owned by big national corporations with (mostly) the same person programming all of the company's top-40 stations. And, like the restaurants, the result has been a homogenazation of the top-40 format to the point where if you live in Phoenix, you will hear all of the same CHR hits on KZZP as you would hear if you lived in Los Angeles and listened to co-owned KIIS. The funny thing is that young people, like with the restaurants above, don't miss the market differentiation of the top-40 format. Why? Because they never heard the originals to begin with. As with the restaurants, today's young people are raised on homogenized radio programming and have absolutely no idea that things could be (and once were) quite different. That's the way it is with restaurants and that's the way it is with radio!