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.
“The only way to ensure a film is going to sell is put Will Smith in it and you open it in 3,000 theaters and make sure we have all the top promotional spots in each venue.”
“The reason can only be this: heroic poetry depends on an heroic age, and an age is heroic because of what it is, not because of what it does.”