Crash Course - Turn Signal

Turn signals normally mean someone wants to merge over into a lane or turn somewhere, right? So if you're behind the driver while in the opposite lane you keep a steady speed and let them merge in, correct? That's how it should be, but where I live it isn't for many drivers.

For some reason when you put your turn signal on while in traffic around this area people will FLOOR IT to keep their vehicle at the same speed next to your car or pass you like it's an emergency. There can be at least four car lengths of room to merge over and this happens. Why do they do this? It's like they think they're in a nascar race and your turn signal means there's an opening for them to get ahead. You're not racing! Stop that!