Because any system where you have to set up conditionals in a "IF THEN ELSE" manner is intrinsically convoluted.
Because you'll have to sit there predicting fringe cases, adapting the script to it, and then learn during the execution of all these other cases your script didn't properly cover.
Any adjustment on the fly will take time, and still none of them will offer you the full granularity of control offered by a properly REACTIVE system.

Don't take it so personally. I'm not saying that the system you put so much effort into is necessarily poor for what is attempting to do. I'm telling you that what it's attempting to do is NOT a desirable result for me.
You are offering me an alternative that in so many ways feel WAY worse than the problem it's supposed to address.

P.S.
Originally Posted by GM4Him
None of these is super complicated or convoluted. It's no harder than the original BG and IWD games where you set your character's basic combat script. If anything, it's WAY simpler and easier to understand.
Ha. Never. AI disabled and full manual control all the time was always the way to go.

I did it in Dragon's Age, tho, and holy shit if after a while didn't get boring when the party was basically playing by itself and the same strategy worked with pretty much anything.