Two reasons. Firstly, there are times when we want to be able to trap orders to other people, which react_before does not. Secondly, the player's react_before rule is not necessarily the first to react. In the case of the player's deafness, a cuckoo may have already used react_before to sing. But it would have been safe to use GamePreRoutine, if a little untidy (because a rule about the player would not be part of the player's definition, which makes for confusing source code). See Section 9 for the exact sequence of events when actions are processed.