Why are convex lenses used in rear and side view mirrors in cars?

A convex mirror always produces a diminished image. Which means the field of view of a convex mirror is large. The side view mirror of a vehicle lets the driver see what is at the side (left side or right side) of the vehicle. The convex mirror helps the driver to see a wider space on the sides of the vehicle. So, a convex mirror is used a side view mirror in vehicles.