Why is the idea of second Brexit referendum such a seeming non starter?

From an American perspective, it seems like there would be a large enough constituency of people who would be worried about the impact of a no deal Brexit, that a second referendum would become a least a real possibility.

Yet it seems from over here there basically is no political will from this. (I know there was a March recently  but it doesn’t sound like that has filtered up from the grassroots really?)