Honesty...? Part of this I think is the fact that the world Square Enix has created is far to small to handle the number of players on a server. Like, if this were a single player game, 30 would seem like a big number. However no one at Square Enix treats the lore as if there are actually thousands of adventurers running around.So they pick a small number like 30 to make the player feel cool for being one of a small group.
Like, I scale everything up quiet heavily. Would the grand tournament between all the Eorzean city states really just be like a dozen soldiers? No, not in my idea of it.
For another example, I think must of us can agree that the Ul'dah in our minds is much larger than the space we see. Our RP's constantly invent little warehouses and alleys and such. Otherwise the Goblet would be larger than the actual town.
Don't worry about the number, it will never come up and it's variable. Scale things up to fit the world we RP in, a giant bustling place, not the small maps with a few dozen NPCs.