It might have something to do with the DJ/dance/sequencer influence on what is today considered pop music
In the house/dance world, having multiple writers has been normal for a long time. The productions were small budget and everyone involved, from the producer to the engineer sometimes got a share by agreement, just because publishing was a reliable, although minor, source of income.
Anyhow, songwriting in the traditional sense of the word seems to be considered out of fashion, as the 'western' concept of melody and harmony.
Beats are now the focus, apparently.. sound design. Both beats and sound design don't produce royalties