I see where you are coming from, but it is imperative that your head moves to see in the blind spots of the car; it's the large section of the surroundings of the car that mirrors are not covering or that are hidden by pillars or other structures of your car if you head stays still.
I don't think it's a big deal if you otherwise check your mirrors, speed, rpm, etc using peripheral vision, but if your head isn't moving and always points forward, it's physically impossible to stay aware of everything happening around you because there are large chunks you never see