I think because by default alcohol is a depressant and also like @bigj75 said, it is easier to obtain. Personally, I'll probably go for hard ciders just for the taste, but I think based on my past, when I made split second decisions, maybe I don't need alcohol to override my SI. With that said, I still rather be safe than sorry so maybe I might have some alcohol before I ctb (not enough to be drunk but enough to lower my inhibitions and even temporarily overcome SI).