Add in the slow but very passionate growth of FM stereo starting in '61. Coupled with the large music industry push of stereo LPs in the same era, there was quite a bit of material to encourage consumer demand and usage. While it was mostly in bigger orchestra instrumental music where the early mixes were intentionally done to emphasize instruments popping out of each speaker, it was enough to get FM stereo kick-started, moving to classical, jazz and even some dreadful big band re-recordings.There were two very distinct periods for FM in the 1960s: Before 1966 and after 1966. Because before 1966, FM was a trademarked technology, licensed by the Armstrong estate. When the copyright ran out, and the litigation with RCA ended, then manufacturers were more willing to add FM to portables and other radios. Two other things happened at that time: The FCC came out with its non-duplication of formats rule, and manufacturing started to shift to Japan. That led to the rise of Panasonic and Sony.
Again, FM stereo began to be pushed in the early 60's in an attempt to further distinguish FM from plain old AM. In the first few years, growth was slow but it was not uncommon to have FMs start off with hours of stereo which were well promoted and often sponsored by record shops and home electronics dealers; some of those dealers would even hold "hear stereo live at Adams TV and Appliances today at 6 PM" events.But there was an audience for FM among audiophiles and classical music fans prior to 1966. It led to the rise of magazines that catered to that audience, such as FM Guide and Audiophile. Some of this led to the rise of the home stereo movement that happened in the late 60s and 70s. The rise of FM ownership and the FCC rule led to new formats and more interest in FM.
FM was also sustained in quite a few markets by the use of a sub-carrier for background music services. An early FM in Puerto Rico was WFID, which usually had no ads on the "public" signal but whose owner had a very profitable in-store music service where they installed the equipment and charged a monthly fee.
Outside the US, in Mexico City a large system of convenience stores similar to 7-11 owned an FM which ran no commercials but, instead, used the SCA for in-store broadcasting where vendors paid to have their brands promoted to the people already in the stores. Similarly, FM100 in Lima did not have on-air advertisers, but had a huge business selling SCA background music services.
The most unusual use of FM is likely the "buscasting" of the early 50's. As station owners looked for a way to monetize their FM investments, one company came up with a system that equipped city bus lines with receivers that played an "in-bus" format that used the captive rider audience as its selling point. That lasted for a number of years, in fact.
Another that abandoned or neglected FM was Storer, which even was slow to monetize its few remaining FMs when it was obvious that AM was in decline. And the passing of Todd Storz in 1964 seems to have distracted that company from developing any FMs in its key markets at a time when they could have just applied for licenses and gotten them "free".There were some groups who failed to see the wave coming. The one that stands out is the Washington Post group of radio stations. They owned WTOP-AM/FM in Washington. They decided there was no future in FM, and donated WTOP-FM to Howard University, a historically black college in Northeast DC. That station today is WHUR, which is consistently one of the top rated stations in town.
But by the mid-60's, a lot of operators were saying "we have been trying to make this work for twenty years and it's going nowhere!" In fact, in 1950 there were over 1000 FM licenses or permits granted, yet by 1960 it was down to just over 600.
It was the new entrepreneurs like Jerry Lee and Saul Levine and Robert Conrad who came in without the 1940's perspective on radio and managed to make a bit of a profit as the band grew.
These, of course, are examples of owners and stations. There are many, many parallel cases of early FM "pioneers".