That makes sense, but I still find it to be an interesting visual phenomenon

At the edge, why are they not just tipping over?

The roots look intertwined, so even trees at the edge are bending roots that are long horizontally.

See also: How wide do tree roots spread.

> Arborists often recommend a tree protection zone with a radius of one foot for every one inch of trunk diameter — a 12 to 1 ratio.

https://www.deeproot.com/blog/blog-entries/how-wide-do-tree-...

They are also pushed by the wind in the opposite direction, i.e. away from the edge.