Are there less ''classic'' audio dramas , how many influential audio dramas are there, and yes I know I am simplyfing this a lot. I didn't know A better way of saying it without losing the point of the question.
The answer depends on what time period we're examining. During radio's heyday, the 1930s and the 1940s, audio dramas had as much or a larger impact on popular consciousness compared to TV and film. For instance, a week after the Pearl Harbor attacks in 1941, about 63 million listners tuned into Norman Corwin's dramatic program based on American values, We Hold These Truths. The most important fact determining impact for most media comes down to the availability of technology at a given time, for both consumption and for broadcasting.
You're right to note that most serialized audio dramas back in the day used to be around 15 or 30 minutes, compared to today's lengths of serialized dramas on TV, which are typically 30 or 60 minutes long. But there were also longer-format audio dramas, such as We Hold These Truths, which were an hour-long, and there were also longer stand-alone works (like adaptions of plays) lasting between 45 minutes to 2 hours, much like films. Arguably the most famous radio drama of all time is Orson Welles's War of the Worlds, which was an hour-long broadcast.
But through the 1950s, the technological impact of radio became overshadowed by the visual medium of TV, which, like radio, provided entertainment in people's private spheres (unlike film, which was, up until the 1980s, were consumed mostly in public spaces). By early 1960s, more than 90 percent of American homes had at least one television set, rendering radio dramas obsolete. Radio dramas required the viewer's imagination to flesh out the characters and scenarios, whereas TV dramas provided that in visual form. It was an easier form of entertainment, and more immersive but less active on the part of the consumer (Marshall McLuhan, of the 'medium is the message' fame, would say that radio is a 'hot' medium whereas TV was a 'cold' medium).
In terms of overall historical impact, the length of audio dramas likely had less to do with the impact of the medium in comparison to TV and films, than with the fact that its heyday lasted only about two decades, compared to film, which has more than a century of history, and TV, which has been widely available for more than half a century. However, there is now somewhat of a revival of radio dramas with the availability of podcasts and other forms of digital media, although its overall impact on culture is nowhere near what it used to be in the 1930s through the 1950s, and is much more fractured. The story of audio dramas is continuing to evolve.
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