Just a theory. A random example (which doesn't hinge on legal vs. right, although it seems to): It's illegal in some U.S. states to change lanes across a solid

Just a theory. A random example (which doesn't hinge on legal vs. right, although it seems to): It's illegal in some U.S. states to change lanes across a solid white divider when driving, especially if you're about to make a turn. There are intersections where the turn lane's solid section is so long, and the block before the intersection is so short, it's basically impossible to merge where it's legal. Especially with any traffic, there's just no time to cross before the solid. But there's room! Once you're in the solid zone, there's no one blocking you. Merging there would be illegal. There's the fully legal option to wait at the light, then go on straight, then turn at a block down the road where the solid is short. But that's inconvenient. You want to get home. But merging here would be illegal. But you want to. So people partition.