That is an argument that has some merit. However, over-timid FOs to exist. Even if he is not afraid to ask the question, an overbearing captain is quite capable of making life hell if he feels his authority is being questioned. So, such a policy eliminates the possibility. Another possibility is a strong FO, who has had enough. ("OK, you stupid old Bu88er - you steer that course - I'll sit back and watch while you get into trouble and learn your lesson").
Flight Safety is a question largely of plugging the holes in a series of slices of Swiss cheese - if you've heard of that metaphor before. This plugs one hole, even where a corresponding adjacent hole should not be allowed to exist.