Indeed, not being able to use ATM is rather a positive thing in my view, however one is still able to use fixed derates which is a very good idea indeed. As lederhosen wrote usually V1 values on contaminated runways are very low, some of them even in the below 100kts area on the 737. V1 to Vr spreads can be rather big and are something one is not really used to on this type so we do brief that in those situations.
However why we are not allowed to use ATM is something where i would have to guess, so i'm waiting on input from more knowledgeable persons there
