Why don't streaming services offer album liner notes?

It’s the labels (i.e., those who distribute the music). When they provide liner notes, the services (at least Qobuz, the one I use) makes them available. It’s really disappointing not to have them for so many releases, and it’s puzzling why small jazz labels, for example, so rarely include good information about the personnel on a release and related information.

You can on the Qobuz app just click on the album and there should be an option so see credits,

Increasingly they are. On Qobuz if you see “PDF” next to the play button the album the album cover and all the liner notes are there. A little “i” and you get a description.