Availability of a limited amount of venues, hotels, planes, trucks, buses, cars, crewmembers, staging, sound systems, lights, video screens, etc, etc, etc. Every possible band and individual artist capable of touring is doing so like never before all at the same time.
Really dumb question, but who is it up to if not Bruce and the band? Not trying to be rude or dismissive. Genuinely curious what goes into the decision.