If we worry about piracy, we should worry about this stuff too.
I'm not saying it's fair but its far from the only sample to have been used everywhere with little recognition and sampling was one of the pivotal revolutions that gave the rise electronic music.
I used to see this kind of thing happen all the time and not just the Amen break.
I don't know the arrangement between the bandleader and the drummer (maybe the drummer was paid by session and was owed no royalties), but, in my understanding, the owner of the copyright definitely was entitled of royalties. In the early days it was chaos but by the 1990s samples were definitely being cleared.
After 1996, when the author found out about the sample, it was used (According to WhoSampled) by Oasis, Skrillex, Prodigy, Dua Lipa, Lupe Fiasco, Skipknot, and in the Naruto soundtrack. There definitely was the possibility of the author collecting royalties from some of those from copyright lawsuits.
On the other hand I remember in various communities since the early 2000s people asking "how do I clear the Amen Sample?", but nobody exactly knew who to contact because nobody seems to know who owns Metromedia Records, who put the original album.
I remember articles and interviews about this from 15+ years ago, so it's weird how no lawyer got in touch with the song author, or how the song author never got a lawyer.
On top of that, Amen Brother seems to contain portions of I'm a Winner and Theme From Lillies of the Field by The Impressions, so maybe that's why Spencer (the bandleader) never got any money to begin with.
I guess we won't know now that both the drummer and the author of the song are dead.