[Bf-committers] Why are modifiers before modified modifiers recalculated?

[gandalf3]

I have noticed that when a setting on a modifier is changed, all 
modifiers in the stack are recalculated, including the modifiers before 
the modifier with the changed setting.
Since those modifiers have not been edited, they should have the same 
result.

If my logic is correct, only the modifiers after the changed modifier 
need to be recalculated.
Why are all modifiers recalculated every time?

-- 
-gandalf3