Why doesn't it actually go through the steps though ? Can't be too difficult, most steps are about going from A to B, fighting something and selecting an option.
I just think it would be easier to actually have the AI try and do each step just like the player would be easier than trying to abstract the whole thing behind a roll (if you want that roll to make sense at least, you could always just put some simple roll check and be done with it but that's just not very good imo).
It's because as quest makers we are jerks. We say things like
You come upon a small farm where the inhabitants are all deathly ill from a sickness
a) Leave the family to die from the plague
spend 200 mana to heal the family
c) search for a cure in the deathly swamps
d) Steal all their food and valuables and then kill them mercifully
Can you imagine the coding involved to make the AI even semi-intelligent at doing this quest. It would be more than it is worth, and to make the quest would be very hard if you had to write "computer code" each time to explain what the option mean to the AI. Don't get me wrong, I'd love the AI to be able to do quests, I just don't see a realistic way to have them do it and to still have quests with open ended text and infinite options.