why do cattleya grow "up"?

[King_of_orchid_growing:)]

The stepping upwards is a result of the nature of having to want to conform to the contours of the tree limbs they grow on.

The way the leaf tip points and the direction where the rhizome grows is usually in the general direction of the light source. If the plant is used to growing towards the light source in one direction, and then you switched the direction of where the light source is coming from, the plant will eventually change the orientation by which the rhizomes grow and the leaves point through the subsequent new growths.

For the sake of argument, if the light source is coming from the right, the leaves will generally point to the right. If the direction from which the light source is coming from is changed to the left, the Cattleya will eventually try to get the rhizome to generally grow in the new direction of where the light source is and have the subsequent new growths point its leaves to the left. This is a simplistic way to illustrate this phenomena btw.