Q #278 - Why are mirrors often slightly curved (convex)?
Although a convex mirror gives a wide view of the scene behind, you should be aware that it won't show you everything behind or to the side of your vehicle. Before you move off, you'll need to look over your shoulder to check for anything not visible in the mirrors.
They give a wider field of vision
They totally cover blind spots
They make it easier to judge the speed of following traffic