Trust me, wind makes a difference. Say I am comfortable at 15°f wearing similar head attire as your photo, ie: glasses, skull cap, helmet, fleece gaiter. I am fine with this attire if the wind is not blowing hard. Take the same exact riding conditions, and factor in a steady 20-25 mph wind and now life is miserable from the neck up. In these windy conditions, I now need a full balaclava head covering and goggles to keep my eyelashes from freezing shut, where as at the same temp and calm conditions, I was perfectly happy with exposed skin.
Drop the temp further, say -10°f. I can usually make my daily commute in these temps using my standard layering of mittens. Throw in a 20 mph headwind at these temps, and now we have to add chemical warmers to keep my fingers and thumbs from losing too much heat before my commute is finished. I would not necessarily want these adjustments without the wind, however, as it would be too easy to start sweating when my hands get too warm, and sweaty mittens can be a recipe for severe discomfort.
I will agree that for some, a windbreaker can solve issues on the torso and legs in windy conditions (although in my experience, this area never gets all that cold anyway, even in windy conditions - with the exception of the crotch), but the extremities will still need to be addressed accordingly to compensate for wind at lower temps.