In a comment on my post Another Introduction to the Bible, Another Chance to Ignore the Farrer Theory, one commenter (James) asks why this kind of phenomenon recurs in the introductory textbooks and he offers some interesting suggestions. Here is one of my thoughts on the issue.
There is a huge pedagogical advantage in making Q critical orthodoxy in introductory courses because it is a tangible expression of participation in proper academic New Testament studies. It is a symbol that one is doing critical scholarship and not Bible Study, that one is engaging in the academy and not the church.
The fact is that Q is not an element in most Christian Bible Studies. One of the big issues for many in teaching introductory courses on the New Testament is in persuading the students that this is going to be different from Bible Study. Q is a bit like pseudonymous authorship of the Pauline epistles -- it is something that some teachers use as a recognizable distinguishing marker that what we are doing is something different, something academic, something critical.
That is not to say that all those who advocate Q do it solely for its pedagogical advantages, of course. Many do it because they have engaged in serious study, they are familiar with the evidence, and have come to that solution. My point, though, is that Q can provide a useful shortcut, a speedy but concrete symbol of the difference between a historical approach and a confessional one.
Under such circumstances, it remains an attractive but also a useful hypothesis.