Don't forget that in 1.0 you could start as a Disciple of Hand or Land, which Limsa Lominsa had 4 guilds of while the other cities only had 3 of them. Back then, all the Disciplines were considered equally playable. That's how it worked out that Limsa Lominsa only needed two combat guilds.

But now that gatherers and crafters cannot be starting classes, and are now NOT considered equally playable, a third combat class needs to be available in Limsa Lominsa to balance things out.