As I said, people will make excuses, people will cite inconsistencies of the first two games.
Yes, the dungeons in Fallout 2 were an inconsistency. And Fallout 1 didn't have dungeons. It had areas, sure, but they were NOT related to the usual dungeons found in videogames. They were actual dungeons in the common pen and paper sense, definitely, but since Fallout 3's dungeons are not that kind, it defeats your argument. No, Fallout 1 didn't have dungeons, and Fallout 2 had a few, and they were alien to the series, as many things in that game. Who actually ENJOYED killing all those rats in the garden, for example?