FBAO is a very party-oriented game. There are a lot of things that you can do much better when you have six people. However, spending your time trying to find five other people who are:
a) of the appropriate level
b) of the appropriate classes
c) not jerks
d) not in another party and
e) not stupid
isn't fun. Isabel and I pretty much only party together, because we're there to play, as opposed to some other people who join a party, then spend the entire time arguing that Naruto could beat up The Hulk, or whatever.
I like the idea of being able to hire a party of NPCs. If you can't find a fighter of appropriate level to join you, you can go to the hirelings guild and rent one. They'd be equal to someone of 90% of your level.
Lets your dancer (or commander or priest) go and do useful stuff without spending half an hour waiting for a fighter to finish what he's doing and come help you.
Lets you experiment and explore without inconveniencing other players. If you want to spend two hours checking every nook and crag in the Space Zone, you can do that. Hirelings are paid by the hour, so they don't mind.
AI won't be very good. It never is. (counter-argument: real people are smarter. That's a feature, not a bug).
It's like admitting that you don't have enough people playing your game. (counter-argument: If you have 61, 601, or 60,001 people online, there's at least one person who's not in a party of six).