This is such a big topic lately, as it should be. I've talked about this on LinkedIn, Twitter, FB, etc., because the artistic side of entire music industry (including how we consume music) is at a crossroads. The labels and streaming services are making record breaking profits and most artists are barely getting by. Selling their catalogs (at least for the ones you've written about) actually and unfortunately makes sense. The fear is that it will become a trend. Touring, when it's allowed to happen again, will help; as will the continued rise in the popularity and sale of vinyl records. These are positive steps but not a full-on solution. The mindset that many people have regarding music is that it's free. They (sometimes) pay their $9.99 a month for the streaming service of their choice and think that's all they should ever pay for music. If that doesn't change, I don't know how or if the trend of selling their songs (and souls) will ever end.
Thanks for writing about this topic!