But this also means that the platforms should have an equal incentive to make listeners listen to longer ones. Spotify seems to pay out about $7 billion / year in music licensing. If they can make the average song listened to by a user just 1 second longer, they reduce that by about 0.5%. That's saving like $35 million / year for each second! Move the average up by 10 seconds, and it's enough to actually make Spotify profitable.
Considering how much of the modern music listening is driven by algorithms either directly or through recommendations, it seems like it'd be incredibly easy for a streaming platform to put a thumb on the scale in favor of the longer songs being what gets listened to. That in turn should make the artists record longer songs. Why isn't that happening?
Or is it happening, and the current state is just the equilibrium we've arrived at when those competing incentives were resolved?