Let us try this analogy. There are a group of quilters and they are a very loyal group. They might find a few more interested people to join their group, but the general population doesn't care. So is the case of "Deep Cuts Radio"
The same with radio formats. You have about (on average) 18 minutes to keep a listener. You better present a product that captures their attention.
Yes, some fuss about repetition (more so now because of articles written by people who know nothing about radio).
The typical radio listener doesn't think about "deep cuts" when looking for a radio station (It has been that way for 40 years). They want a song they like (usually the dreaded researched stuff), and something they know well.
NPR is a good example: They have a wide variety of music choices... world Music, instrumental, folk, new songwriters...but yet, they barely make a dent in the ratings. I bet if a group of 25-54 women had to choose between their NPR station (for music) and their local AC station...AC would win.
There is a documentary trailer about free form rock radio that just came out on youtube (I can't find it now). It has a bunch of legendary Disc Jockeys talking about what they played, and there were no rules. (If somebody can find it, please post it). There was one problem, ratings were awful, and revenue well.....
This concept lasted as long as it did because most owners at that time could care less about their FM's (they were duds for the most part).
All of a sudden you has stations like WABB in Mobile, and WHYI in Miami signing on. Listeners were abandoning AM to migrate to this new FM band. Meanwhile, owners of these "B-EZ" and "free form" stations were taking notice.
...and that is today's meaningless dissertation.