Tim Burke takes up a student's question: if academic cultural critics understand expressive culture so expertly, why can’t they create it? He maps out the variants of answers that cultural critics give.
I myself have had very limited filmmaking experience (essentially one class in college making silent super 8 films) and, teaching in a production department, I'm keenly aware of the asymmetrical expectation I have of my media-making students to do some version of what I do when I am not really able to some version of what they do. My own reasons encompass a number of the reasons on Burke's list. Of these, reasons #3 (the autonomous logic of criticism), #5 (criticism's emphasis on explaining phenomena external to the cultural work), and #7 (the money and technology required for creative work) loom large.
I would add, for most media production, there is no single "maker's perspective." Division of labor means that writers, gaffers, production sound mixers, and assistant producers all have specialized jobs and abilities. Moreover, even within one role, the scale of production may be crucial: one can learn about framing with either a portable video camera or a 35mm camera, but in most respects these are radically different arts. Which activity should a film or media scholar do to best get the creator's perspective? This question needs not necessarily negate the utility of gaining a creator's perspective, but it suggests that there is no obvious starting point or scope for theory-praxis ambidexterity.
Note that most of the reasons Burke gives are ideal, not practical, while in fact the structure of educational paths and academic professions tend to provide a better ultimate reason for why cultural scholars so rarely gain knowledge as creative producers. On one end, all but the most ambidextrous of creators will find themselves discouraged in the path of graduate education for having an incompatible sensibility with pure scholarship. On the other end, the incentives of the profession do not reward scholars with production/creative experience, and to the extent that professional activity is a finite resource, the time and effort spent on creative work takes away from that spent on scholarship.