There is a certain ruthlessness in the way the AC/DC organisation does business. The rhythm guitarist and lynchpin of the band becomes mentally ill - no matter, get the cousin to play. The drummer becomes a criminal law fallacy - ooops, get the old drummer back in. The singer with 35 years of combat duty loses his voice - hey, someone call Axl! Next, Steve Jones will dep for Angus and Steve Harris assumes Cliff Williams' duties. It will, of course, still be the full AC/DC experience.
The Scorpions just had to call off a bunch of German dates because Klaus Meine's lungs and vocal chords are inflamed, there is no talk of getting someone else in to sing. Is Klaus Meine more important to the Scorpions than Brian Johnson is to AC/DC? Likewise, I couldn't have imagined AC/DC's musical chairs with a band like Led Zeppelin: Could you envisage a Zep reunion tour with say, Bonham jr, continuing after either Jimmy Page or Robert Plant become road casualities? Or the Stones continuing a tour with off-the-cuff replacements for either Jagger or Richards?
Milking the cangaroo for what it's worth. The institution taking care of Malcolm can't be that expensive.