The inherent problem is that, if one is successful in creating this waking habit, it will still be a habit (something that happens without much conscious direction). This could result in you touching all of the door frames in your dreams, but not gaining lucidity because you are so used to doing this while awake. The reason why reality checks work is because you sort of "snap yourself out" of your waking habits to test the nature of the reality you find yourself in. Thus, the dilemma with making any reality check habitual is that you run the risk of loosing the original reason for even doing reality checks.