I always got this sort of vibe that there wasn't much leading done in clans, that it was more of a group of people that just ran around killing shit/solving people's problems for fat wads of cash, unlike FFT where it's about Ramza and his struggles with politics/the church/family/assassins with stop bracelets.
I guess when Luso noticed that the journal fills itself out, and that it's apparently his ticket home, he concentrates on just working in Ivalice while his journal completes itself. The plot sort of throws him into a cage, and he realizes that the only way to get out is to stay in the cage for 70 hours or something. So he decides to make the most of out of it and enjoy his time there. Cid probably thinks he's an interesting character and has taken him under his wing, so I guess he's like an apprentice while the other clan members are just lackeys.
The only reason I'm somewhat defending the ffta2 storyline (and I do agree that the writing is bad) is that later in the game it becomes evident that Luso is overworking himself, to the point where the important fellows in the clan are always telling him to slow down and chillax. I think he wants to go home, badly, but he just doesn't talk about it.
Ugh, why am I analyzing this shit.