If I were to speculate, I would expect the number of times a song is played most likely to adhere to a power law and therefor this average number of streams is not an ideal measure.

And yes, I'd would expect the tail to be fragmented. Lots of people listening to but a small and mutual exclusive set of bands. Next to the odd main stream one.

So perhaps it is not really a question of light users sponsoring heavy ones, but more the banality of average taste.

Would love to see some stats.