It's not just the east coast.
Even if the local grid is in good shape it's not uncommon for the park to have substandard service. Particularly older parks. 40yrs ago, a lot of RV's didn't have air/con or only a single air/con. Now it's rare not to have air/con and 50 amp units using cheater cords to pull from 2 outlets, means the systems are under much more strain when it gets hot out on a busy weekend.
Last week, we dropped below 107v (with the autoformer boosting voltage), so we broke out the genny. The owner came by and had no answer when we told him provide us the 120v-30amp power we contracted for, so he moved on.