Why do you think the family I nanny for always has the curtains drawn?

There could be tons of reasons. They could keep them closed because the sun makes it hot in the apartment, they could be sensitive to bright light (eyes), they could have expensive furniture and paintings that could fade in the sun, they could hate the glare on the TV from the light, they could be fair skinned and super sensitive to direct sunlight. See what I mean? Tons of reasons. If you really want to know, just ask them. I am sure they have a pretty good reason.