These veins prefer to grow up and over buildings. Am I stretching this? I hope not.
But, veins prefer to grow up against gravity and grab on to the wall.
Dictionary.com says:

1. The selecting of someone or something over another or others.
2. The right or chance to so choose.
3. Someone or something so chosen

Do these veins prefer to grow the way they do, or is it scientifically engrained in them. [I really hope I'm not stretching this idea.] Is their right to prefer to grow the way they do scientifically/biologically explainable? It's not really preference, but probably just nature. Veins just naturally do this - they are able to grow because of the xylem and phloem and etc.