Originally Posted by
MrLion
First of all calm the f**k down.
Secondly, while its true that it is a video game, that doesn't mean that it'll abstain from things in life, especially in an MMO where you're not really the "superhero" of the game like a single player (and many people want it this way but it just can't), when in reality its a community driven game.
With that said lets turn over to other MMOs, let's start by one that you probably know already since you're a noob to this game, WoW. In WoW, there's two factions at war against each other, Alliance and Horde, you pick one...why would it make sense to be able to join both in one character? It doesn't...well unless you fall prey into Blizzard's horrible business and pay 25 dollars to change faction.
Its the same design here in FF14 with the Grand Companies, if you payed attention to the story and not hit enter many times in cutscenes to skip them, the Grand Companies are not really allies, but they're not hostile to each other either. Therefore it doesn't make sense to affiliate to more than one Grand Company.
Does that answer your annoying questions?