"because it feels like it"
i've got one that's trying to reach up and strangle itself with its own aerial roots. -sigh- then i've got another one which put out a bunch of aerial roots, over the top of the medium and the edge of the pot and started to wander off---all in the same direction. the leaves are growing in one direction, and the roots (about 5 inches long) are all cascading over the edge in the other direction.
then i have one that has grown several aerials which bifurcated at the tips and are growing like elongated Y's. then there's the one that grew a couple aerials in different directions, down over the sides of the pot, and are trying to stick themselves back in through the holes in the bottom. aerial roots are cool.
(you gotta watch 'em though, or they stick their roots in each *others'* pots.)