Just setting this sub up for another penis waving contest because NV does not have this issue. The good thing is that 3 doesn't have this issue as much either. 4 is just the most egregious because first of all, voiced characters makes it much worse when you hear the distress he's experiencing because of the loss of his family, you can't just RP that you don't care that much when the pc says 'all i care about is finding my son'. Secondly, 3 and NV didn't have building and you can't lock off building until you find your son because open world fans would bash that even harder, so you're left with a little RP hole in that I can discover and build every settlement in the game before finding Shaun.
An interesting point, however, is that Fallout 1 definitely DID have this issue. And Fallout 2 didn't, because the devs noted fans disliking that. Fallout 1 literally had a timer set for you to save your vault and if you didn't do so you reached an end game state (fail state). They acknowledge it doesn't bode well for open world games so no restriction was applied to Fallout 2. You could explore as much as you want, no penalty.
So the issue is Fallout 2 and NV (and to some extent 3) learned from Fallout 1's failed design. But the latest game Fallout 4 went steps backward in that regard. If you want to see ideal narrative in this series (or any games) look up Fallout 2 and NV.