What is line?
Is it only an infinitely-extending one dimensional figure? If instead, you consider it as an abstract form, then line is wilder, and more interesting. If this abstract symbol is allowed to curve, lean diagonally, or lay down horizontally, the line can become all sorts of interesting things in our art.
If we only consider straight lines, we still have an interesting beast. I took my camera and went in search of naturally occurring ones. I’ve included four. The concrete walkway, a box of business cards, siding, and a door, all had straight lines dominant in their design. If you look around where you are right now, you’ll find many marching through your life like tin soldiers.