I have attached a video below of what traffic looks like in major cities such as Hanoi. From first-hand experience, I promise this is extremely authentic. For a while, I was afraid to even cross the road!
https://www.youtube.com/watch?v=Uz5uxAsrbwI
Motobikes provide easy and quick transportation around town and there are some rural roads in Vietnam that are too small for cars to access. Similarly, as mentioned previously, a substantial amount of people in Vietnam do not have the finances to afford a car.