The reason why those cool stuff as Geki listed still remain unreleased is they wanna keep it for future releases. the moment LP disband (maybe one day), labels can still making money from that vault. Imagine if they give everything they have now, what's left for the band in the future? The labels surely wanna make more money. They're getting old too, dont think they will be fit enough to make more materials like few decades ago. So, yeah. Box Set for their discography we might not get it anytime soon.
Even Metallica releases their box set after more than 30 years in the entire career. We're lucky if we get one.