The worlds associated with alien phenomena are too diverse, for example, those medieval-type worlds with low technology levels—if the environmental adjustment in such a world is also very "harsh," then there's no need to consider any follow-up actions in that kind of world.
Even if there are castles or towns near the alien phenomenon, at most, one could acquire some wealth or similar things, but those are exactly what Ahn Seven needs the least. Not to mention wasting time, there's also the possibility of Alien Phenomenon hunters being left in that world should the phenomenon disappear.
It's not worth the risk for some antiquated gold and silver treasures.
