Alain has had a back injury that has been recurrent and unpredictable : he mentioned in an interview after leaving the band that there were multiple occasions that Moz came very close to cancelling shows as Alain couldn't play/carry a guitar - getting slapped on the back on an American tour by a fan caused a recurrence of this in 99? 02? It could be that this happened again in the midst of a big tour and "the show must go on", to coin a phrase.
I'd been wondering along the same lines. Did Alain's recurrent back injury leave Morrissey /his management unable to obtain insurance for the various tours and, hence, liable to massive out-of-pocket expenses from enraged promoters/organisers should a multi-gig cancellation occur ? It would be nice to know (officially , for once) what exactly went on...