erm side view mirrors have always existed. Why do you say not ?
Only in the very VERY early cars with no tops when there were few cars on the road and the driver sat high and on his own and could readily look round.
Agree that once fixed windsheilds and clear rear windows were widely deployed that the interior rear view mirror often relegated the side mirrors to "options". But in the 50s and 60s everyone fitted them
"A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'