When I edit a plane with an image texture it distorts oddly I'm just scaling (pictured) a single plane, with the left-side edge but the scale of the texture doesn't scale properly . . why does this happen? This is just a single plane with a simple plane UV (smart UV)
There is a smiple fix: add a sub surf modifier and set it to simple. Be sure to increase to subdivisions.



The issue is that because a face is made of 2 triangles, the uvs are stretched across the triangles and not the mesh.