If you're playing a Catholic power not capable of winning a crusade singlehandedly (i.e. not England, France, HRE), under what circumstances would you still join a crusade, if ever? Would the Pope mind if you join his crusade, send your troops so you and your heir get the crusader trait, then send everyone home without fighting a single heathen? (Sounds gamey but I'm tempted to do this to nullify the "not crusading" malus)
Somewhat related: Post 1.05d/e, is it normal for France and HRE to get embroiled in civil wars more often and thus not join any crusade at all? In my current game, it seems none of the 3 majors join in the Pope's crusades so he just fails all the time. Spain is all muslim, the Shia Caliphate is slowly eaten up by the ERE.