Adding lights as decorative elements helps set a mood in a space. Provided that general lighting is already installed using lights instead of wall art can be a decorative way to provide ambient lighting.
It’s important to understand that even on a sunny summer day natural light from a single window is not always sufficient to thoroughly light a room and of course this is especially true come nighttime. Additional light sources near your window will allow you to subtly fill out the light scheme and achieve a balance so the space feels beautiful at any time.
Adding lights to stair risers is beneficial since it can be hazardous negotiating stairs especially at night. Staircases are often enclosed so light them from the sides or embed lights in the risers as a design element.