Tons of great music. When they rejoined Maiden it was a glorious tour. These guys played songs from a vast catalog that's still one of the greatest runs in metal history.
I love early Helloween, and some of the 90s-era Deris stuff, but Deris singing isn't a reunion. I'll be happy to see this live, but all of Kiske's best stuff is contained on two releases.
I suspect the vast majority of people buying tix feel the same way. We don't want to hear anything from Pink Bubbles Go Ape or Chameleon, we want to hear Kiske singing songs from Keepers I & II, and Kai singing Ride the Sky. When I heard about the reunion I heard the chorus from I Want Out in my head. I didn't hear Kids of the Century.
Sure, I'd also like to hear Deris singing stuff from Time of the Oath, and Better than Raw myself, but they likely play songs from those recordings on every tour.