Import and Share in many Configurations
Since JR5 is able to import songs from soundcloud, youtube, vimeo and many other content networks, the playlist can make a great way to tie all that content together.
One user imports a bunch of songs from youtube to display on their profile. That content can then be used by other users to include in their own playlists.
This makes it possible for a community of music lovers to get together and create a music site around music they love without actually having the bands present on the site.
Where JR4 tended to be a community of bands, JR5 can be a community of fans.