One of the dire facts about light pollution is that darkness is so fragile. All it takes to ruin a dark place is one light.
To take one example from personal experience, one of my favorite spots to observe when I'm living in my city apartment in Cambridge, MA, is a public park called Robbins Farm in Arlington, MA. It's just 7 miles from downtown Boston, so the skyglow is huge, but within its suburban context Robbins Farm is delightfully dark -- usually.
There are perhaps three or four dozen houses fronting the park, and the lights shining out their windows are readily visible, but I don't find them particularly annoying. But there's one house with a bright, unshielded porch light, and when that light is on I can't look in that direction without getting blinded. So I lose a whole sector of sky.
At locations far from population centers the situation is far more dramatic. It takes a fair amount of light to ruin a suburban park that's already bright from skyglow alone. It takes nothing but a bright flashlight to ruin a pristine location.