What we saw instead is Lightning having tantrums over her sister's choice in husbands (not relevant to Bart trying to drop Cocoon), Hope irrationally pinning blame on Snow and trying to kill him (hardly a depiction that indicates strong motivation for wanting to save humanity), Vanille providing lots of annoying fanservice, and so on. Compare: at Mushroom Rock in FF10 we learn Wakka's brother joined the Crusaders and died fighting Sin, giving Wakka and Lulu (the girl left behind) the motivation to fight against Sin. The big event at Mushroom Rock shows the futility of fighting Sin in an alternative way (to the Final Summon), and Tidus also confirms the 'feeling' of his father in Sin. Character plots and events that bind to the main plot of completing the pilgrimage and defeating Sin. The first half of 13 is certainly flimsy padding in comparison. 10 reveals the backstories of its characters along with the world; 13 clumsily cuts around and shoves in flashbacks to flesh out character backstories...that reveal nothing about motivations tied to the main plot. It's hardly a wonder that Lightning, Snow, Hope, and Sazh readily abandon Cocoon and then fade to the background when they hit Pulse.