Cars don't just appear out of nowhere. They are for the most part highly predictable.
I should add the caveat that I am specifically talking about Western countries where traffic is quite orderly. In Thailand we had to cross multi-lane roads by just walking into traffic while traffic weaved around us, they wouldn't stop for us even at crossings unless there were lights. In this situation you don't have much of a choice. Here in Norway, cars will stop for you so there is no need to walk out until you are sure the car is stopping. Some times if I'm crossing a multi-lane road I'll walk across one lane then stop and make sure the car coming in the next lane is also stopping for me. Some times they don't. I look both ways even on one way streets.
I've had many situations where drivers clearly don't notice me, and since I didn't walk in front of them I'm fine. Also had a few situations where someone I'm with walks out and I pull them back just in time to watch a car/bus pass right in front of them.