I look at it like a piece of steel. A short piece is very rigid, but in a very long piece it bends like spaghetti and the longer you go the squirmier it gets.
Wind and gravity both play into the equation. They are fixed variables but one end is fixed and held rigid, so the farther away you get from the point that is held fixed you overcome the tensile strength more and more to hold it straight so you will get a curve. Said curve will not be constant. It's like a fulcrum and a lever. For each increment you move away from the fixed point you are using a longer lever. Wind friction is the lever that works against the tension and gravity.