Among the arguments against allowing business unit generalist lawyers to handle litigation is that they are not practiced in the arts and they may put litigation on the back burner when the choice of how to spend time includes getting deals done. The managers and executives they support are not interested in resolving old mistakes that fester as cases; they make bonus based on what they sell and service.
Analogously, if lawyers who supervise law firms on litigated matters are allowed to take depositions, prepare and file pleadings, and argue in court, they may let slip their other responsibilities to supervise those outside counsel, whose role it is to do the front-line litigation.