It absolutely would not. AFAIK even 0 glossiness reflection still computes reflection rays. So you would have a material that defaults to pretty much diffuse material, but is a bit slower than current diffuse material for no reason. Simple diffuse material should be a default, and if that default would ever change, it would be sensible to have reflection at 1.0, but glossiness should stay 1.0 as well, so new people are actually aware there is some reflection going on.