I find it unsettling when, outside in the dark, that is in the evening/night, there is a bright surface in the window when you are inside. That’s why anthracite, matching the window frame on the outside.
It can be just as unsettling the other way around: during the day you then have a dark mourning border around the glass, especially if the walls inside are also light. And I think during the day you look outside more often because at night you don’t see much anyway or the shutter is already down.
Since dark window frames also heat up more in the sun in summer, the frame could possibly warp; at least, this argument is often heard. However, whether this is still relevant today or whether the frame construction has improved, I cannot judge due to lack of experience with dark frames.
I think the color is also subject to a fashion trend. Most people follow the current trend, and when it changes again in a few years, they want to have everything different.
By the way, my neighbor is currently painting his dark wooden windows white. It’s simply a matter of taste. If I were building new, I would pay more attention to an overall harmonious appearance.