Lectio Brevior as Mental Shortcut

J. R. Royse's useful book on textual criticism contains a useful insight about the reason for the popularity of the rule of thumb known as lectio brevior (the shorter reading is preferred). Basically, this rule of thumb says that given two manuscripts that disagree, the text with the shorter reading is to be preferred. Rouse argues from empirical evidence (and I concur though I reached the same conclusion through a different route) that scribes tend to drop things out rather than add them in. So using lectio brevior is more likely to give an incorrect reading than taking the longer reading. In the quote below, he argues that using this rule of thumb is an excuse for textual critics to avoid using their brains:

The frequency with which scholars such ash Hort and Metzger appeal to the preference for the shorter reading is doubtless in part due to the ease and objectivity of its application. Whether a particular reading fits the style of the author, is grammatically smoother, follows Semitic idiom, or is theologically more acceptable, is usually very much a matter of debate, and reaching any decision on such issues would involve the weighing of a great deal of evidence But deciding whether one reading is shorter than another is, at least usually, a perfectly straightforward task. It is therefore convenient to reduce textual questions to questions of length, and then to decide accordingly. (James R. Royse, Scribal Habits in Early Greek New Testament Papyri [Atlanta: Society of Biblical Literature, 2008], 711.)