If piracy is moral and ethical and enables us to share knowledge, why do private trackers gatekeep this knowledge? It goes against the principles of piracy. Do they do it just to feel superior about bring in a sekrit club?
I would say it is more of a practical consideration. Private trackers generally enforce upload/download ratios. This ensures the health of the sharing pool stays good.
Don't know what are you talking about, I was seeding on Rutracker, NNMClub for 5 years, giving 10-15GB day sometimes, I've seen many profiles who share 6-10-15 TBs a day, just a couple days ago a guy was asking on qBittorrent discussion how he could improve his 18Tb home seedbox, he had to open different instances of qBittorrent Enhanced, because at 10-15k torrents it was bugging out.
Their moderators contribute relentlessly, there are annual topics with competitions for best drawn picture, sang song, written poem, word games etc..
There's a thing called Torrentovka, when people from Rutracker meet and camp, telling stories, many couples were found and married this way, Rutracker is basically a family forum.
Hell, my girlfriend uses NNMClub, we were both seeding Kaleo once at the same time :)
Health comes with morality, it shouldn't be mandatory.
Usually torrents remain seeded because private tracker users are encouraged to seed everything forever. In addition, often if a private tracker has a bonus system they will offer extra bonus points for seeding low-seed torrents, and some even automatically mark torrents as freeleech if they're below ~5 seeds, encouraging people to revive its seed count in a targeted manner.