Because I don't think people understand that you're going to have to build up fast...
The Clan have more than
fifteen units built this turn to start. Plus, for every one of those units, they get a free unit of str.2 Goblins - weak, but there are a
lot of them. They are, perhaps, an exceptional case but they still prove a point.
The point is,
you may not be able to survive if you don't draft. Don't expect to be able to build up your forces slowly through the economy. You may have a neighbor who doesn't want to worry about that, and will instead just draft to his limit and invade. I'm not saying that you
can't try to play it slow, but that it's risky.
(
Jopa: Don't panic. 
)
EDIT: While I'm at it, hopefully this will also put the characters into some perspective. Sure, they're random and annoying; but they (probably) can't raise an army to destroy and conquer you. Secure your home base before you worry about hunting down any of the measley ones.
Now, on the flipside - characters! You're not going to let news like this show you up, are you? You want your names to be mentioned with
fear - or at least respect. Do something cool, and show that you can be just as influential as any stupid thirty orc units. I bet they're not even all that tough.