There's a shitload of valuable vinyl records that don't have any art at all or even any cover. Paper and cardboard doesn't last as long as the record itself.

No, the reasons for this are entirely technical.

de gustibus non est disputandum

Look, I am telling you about my own lived experience with collecting vinyl. You can speak for yourself, but I carefully stored all my items in archival sleeves, and the jacket, art, and inner sleeve were often just as important as the disc and the music encoded on it.

There was a real thrill and reward that came from collecting LP albums in particular, and that meant 12" discs, and I also had a particular specialty in finding 12" remixes and DJ versions of singles.

Yes, there were shaped discs, and colored vinyl, and white-labels and acetates that came with no art or plain sleeves, and I collected those with just as much alacrity, but it really was a pleasure to flip through my collection, or someone else's, and drink in that large-format album art.