Tucking hair under sweaters and coats. A trend? Or a way to protect hair from cold weather? 

Certainly a trend. We have been hiding hair under scarves for a long time now, having wrapped in them so that you can only see eyes and forehead. We did hide hair under coats as well. But not that often did we hide it under sweaters, turtlenecks and shirts. Now it became quite popular, such a massive trend.
Firstly, it's convenient. If you neither have a desire nor time to make a "serious" hairstyle, moreover, you are tired of ponytails, then you can safely hide your hair under clothes. Secondly, it's interesting. By hair tucking you can add some French charm to your look, but at the same time you can try another hair length without cutting it. After all, each of us, at least once, wanted to just cut these centimeters, right? I do have my own experience of cutting hair short, some 2 times. Although, if we consider that my hair were first cut short when I was 6, then it accounts for 3 or even 4 times. Since I'm on the stage of growing my hair super long, I literally fell for hair tuck trend. And, thirdly, it's certainly a reason to protect the ends of your hair from cold. Who wants to harm their hair deliberately?
That's how following this mass trend, mostly European-based, I decided to hide my hair under turtleneck. The last one, incidentally, is among season's trends as well, in combination with coats and blazers such a tandem will look amazing. Two in one - keeping warm and staying in trend. I supported this combination with bright leather pants, court shoes and short coat, that reminds more of a jacket. Simple, but with French touch.

Look of the Day:
Vintage coat
Promod turtleneck jumper
Sepalla leather pants
Zara asymmetric strap court shoes
New Look croc print flap saddle
HultQuist pendant necklace