Well, lots of stuff gets re-released now and then, like currently Morricone's BLOODLINE and JANE EYRE and HEIDI... even though they are available from Discogs etc.
So sometimes all it takes is to wait for a newer, updated release. Especially popular composer/titles get often re-released.
Presumably, most film scores will at one point in time be re-released, either as CD or streaming/digital download. (Like FUTUREWORLD is currently available from Apple, though I don't buy lossy downloads.
I wish La La Land would re-print their Superman II/III booklet and send me one and re-design their 3-CD set cases so they don't damage the booklet inside. They should send me their re-designed 3-CD set case with the label for this title already installed. Their current cases do in fact damage the inside booklet.