Based on this logic should we also randomly pick some skills our jobs have to simply not use to make things more challenging? Next WP i run as tank ill avoid using Flash, or on healer ill only use stone skin and Medica2 nothing else. My point being we use the abilities given to us to do a job, Limit Break is one of those abilities. That being said its not like Limit Break is some game breaking ability that one shots boss mobs simply wraps up the fight with a nice big BANG YOUR DEAD!

p.s. the damage Limit Breaks also look hella cool to so that's a reason on its own =)