I'm starting to think it's a cultural thing. Why do you and other people think that not having natural light is depressing? When I see people from US or some other countries talking about lighting, they seem to almost worship natural light.
I'm living in Sweden, and at least in the northern parts some people do get clinically depressed during the very long and dark winters. Maybe if you live in e.g. India, southern Europe or Australia, you have enough sun to never really miss it. But when sunlight is scarce, it definitely affect you.
The the extreme example of this is seasonal depression, which is the reasons Scandinavian countries have very high rates of suicide.
But good scientific studies show most people are effected by lack of sunlight, and it impacts mood and alertness.
Windows in offices is an expensive problem to solve, but as sunlight frequency strip lighting is the same price as the yellow stuff normally seen in offices, I'm surprised we don't use it.
