This exact problem has prevented me from creating playlists in the first place. I'm a non-iphone Apple Music user, but the same still applies. I have no playlists because I assume I'll lose all that curation work someday. So, I just don't do it.
I wonder how many others are the same way and how that negatively affects their revenue.
Totally understandable... because playlists are tricky.
I have a medium sized local music library and up to a few months ago have used an iTunes-like app to manage it all. Then I decided to move my music library... everything was still in the same folder, just on a new server but the playlists were all empty. I certainly was a bit freaked out when I realised that the m3u playlist files contained absolute paths to every song, instead of relative paths. Turns out that the player/manager I had used did that by default... took me a few weeks to correct everything!
I sometimes envy people with vinyl or cd collections, must be easier to deal with...
I wonder how many others are the same way and how that negatively affects their revenue.