And if that is what users want, then those tracks will get a lot of plays, and by extension payment. Shorter tracks would also mean users have more opportunity

And if that is what users want, then those tracks will get a lot of plays, and by extension payment. Shorter tracks would also mean users have more opportunity for listening to a variety of songs/artists. A single user can only listen so much in a day (capped at 24 hours, and more likely 12 hours if they aren't doing some kind of phantom streaming). This would then ultimately dilute the payments to artists releasing a large number of shorter tracks.