"Empty" windows without curtains are only allowed for Scandinavian style or loft style. In other cases, you should not refuse to decorate the windows, as this can deprive the room of comfort, and the interior will appear incomplete at the same time.
Windows take an important part in interior design, so the decor for them should be selected with great care.
Each style has its own requests for the design of window openings, but the presence of curtains in the design of premises is almost always an indispensable attribute.
The only exception to the rules, when the decoration of windows ceases to be a mandatory attribute for any of the modern styles, is the presence of a stunning panorama outside the window.
After all, you will agree that the view from the window itself is much more important, for example, on mountains, sea, forest or a beautiful lawn, which in this case will serve as a perfect addition to the design of any interior.
In such cases, even try to make panoramic windows, and to "erase the boundaries" between the interior and the street, with even a floor covering made the same outside and inside.
If the windows face the end of the building with a gray faceless high-rise building, or, far better, in the backyard of a private house, in this case the curtains will serve as a wonderful decoration in the interior design.