Why do knights move in an L shape?

Why do knights move in an L shape? With the L-shape maneuver, it has access to eight. Also, if it only moved two squares, straight or diagonally, a knight would always be restricted to the color squares that it started the game on. With both of these, such a piece would be considerably weaker than its minor piece counterpart, the bishop.

With the L-shape maneuver, it has access to eight. Also, if it only moved two squares, straight or diagonally, a knight would always be restricted to the color squares that it started the game on. With both of these, such a piece would be considerably weaker than its minor piece counterpart, the bishop.