Lines in Architecture

What is it about lines in architecture that are so aesthetically pleasing?

I don’t know if it’s the engineering background in me, my ocd-like need for symmetry, or just the simple beauty of a structure or space with clean lines that draw the attention of the viewer, but I love lines, especially in architecture.

Maybe this is because, in photography, lines are often attributed to human emotion:

We may find that we are subconsciously drawn to subject matter whose lines "align" with our mood! This may also be a link to our attraction of various design styles in architecture.