As others said, it's entropy. Basically, think about the ways that you can arrange your lines in a box. There's relatively few ways that you can arrange the l

As others said, it's entropy. Basically, think about the ways that you can arrange your lines in a box. There's relatively few ways that you can arrange the lines so that they're neat and not all tangled up. There's a lot of ways that they can be tangled up. So if the lines get jostled and move a bit, it's more likely that they end up in a slightly more tangled arrangement than in a less tangled arrangement. Do this a bunch of times and your lines end up all tangled up.