People should look in cars, and actually most do.
I bet you're in disbelief of that.
We all look, but we don't always see. The quicker the look, the less you see. There is a thing called a saccade. This is where your eyes only see something when they are still, as you move your eyes you only get snapshots of the panorama. Your brain makes up the bit in between that gives you a sense of a smooth panning motion. The other thing with your eyes is that you actually only see a small part of the vista in clear focus, the rest is a blurred picture and your brain deals with the rest. So yes, they look, but they don't see you. You do it too on your bike, but as a bike rider, you're better trained to look better, but probably not as much as you might think.
So why rely on a car driver to see you? Don't, put yourself in a better position to be seen, and more importantly a better position to be able to deal with someone pulling out.