THE concave mirror has wider perspective, but it distorts size and distance.
Is there an international rule prohibiting a car maker from installing a
concave rear view mirror as standard accessory ?
If not, why are the car manufacturers not doing that ?
I think you mean convex mirrors !
There are no regulations prohibiting the use of convex mirrors but you
will note that on the mirrors, there is usually a statement informing the
driver that objects appear smaller and may be nearer than they appear.