My theory, at the risk of sounding like RLonger, is that the band didn't think a full Senjutsu tour would go down very well after the criticism
they received on the Matter of Life and Death tour and first leg of the Final Frontier tour. There seemed to be less of it on the Book of Souls tour, but I think that was more down to everyone being glad to see Bruce fighting fit after his cancer scare. Couple that with Senjutsu not hitting the top spot in the UK and somewhat mixed responses to the Senjutsu tracks on LOTB and they probably decided they needed something to draw in classic fans. Can't do a history tour on top of a history tour so, fuck it, we haven't done SiT yet, let's go.