It probably has everything to do with the motivation of the authors. The driving force behind doing research for publication in name-brand finance journals is to obtain tenure, promotion, or (more generally) higher status in the academic community, including the possibility of moving up the academic food chain to a better school. Relevance to actual practice or, for that matter, to teaching is only important to the extent that the editors and their hand-picked referees emphasize it in their accept/reject decisions. As I think you imply, that has not been the hallmark of finance journals lately. I am not at all sure how much worse this is in finance than in other fields, but (as TJ is likely to remind us) an academic finance career can be extremely lucrative compared to other fields of study, so the incentive to play the game by the rules and not rock the boat can be pretty compelling.