My guess is that if they now choose to change of director for every other film, it's just because you can't really change the formula, you can merely try to film it your way.

He made 22 films from the 1950s to the 1980s including four James Bond films. Guy Hamilton (born 16 September 1922) is an English film director. Remaining in France during the Nazi occupation he was active in the French Resistance.