I think the placement of things in NV is also not as good as FO3. When i was playing FO3 i keep finding new quests or places to explore when i try to do the main quest. Just following the broken roads often lead you to places like the Nuka Cola plant.

In my time playing NV so far, i haven't really diverge from the main path and it seems like i have to purposely want to explore in order to find stuff. My favorite thing about FO3 was randomly finishing objectives or finding item for quests i didn't even know about.