I'm not a Forgotten Realms fan and haven't owned anything related to it, other than the Starter Set, since owning the 3E FR Campaign Setting.
But as presented, Phandalin is surrounded by trouble and the town is even under siege from within. Running to get help would mean days of travel through at least somewhat hostile territory (after all, the goblins stopping cart traffic on the main road is the start of the adventure).
If one zooms back, no, not a points of light setting, but for someone like me, who's just run Phandalin in isolation, it definitely works that way, IMO.