Well, I don't think this is clear in the official canon, but I always took it to be that the DAA puts monsters in dungeons as protection mechanisms - not always, but sometimes - and smitemasters are called in when the monsters get out of hand, which always happens, sooner or later.
Plus (spoilers for the ending of JtRH follow):
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×The empire and the DAA are clearly cooperating with each other to some degree, as indicated by the job offer Halph gets.
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I got my avatar back! Yay!