It is very likely that Cardassians are semi-nocturnal as well as semi-crepuscular. Now, lemme back myself up, here.
Cardassians are reptilian, meaning they are cold-blooded to some degree, and thusly need heat to remain comfortable and healthy. Now, lots of reptiles are fans of bright lights because bright lights = heat. But, there are reptiles that sleep a lot during the day, sunbathing, and hunt at night. This isn't to say that they aren't active at all during the day, but it's really the best time for them to catch some Z's.
Cardassia is very bright in some scenes, yes, but there are also scenes where the natural light appears to be a murky red color. One could say that this was due to a sunrise or a sunset. If that's true, it supports the idea of Cardassians being crepuscular (awake during twilight hours).
We see Deep Space Nine as Terok Nor in the past, while Cardassians are still running it, and it is very dark. Nighttime dark. In every scene. It’s also pretty steamy in there. So when Cardassians have the ability to completely engineer their environment, they make it dark and humid. They would probably function very well in a tropical rainforest. Seems nocturnal to me!
So, I offer as tribute: while Cardassians can and will go about their business in broad daylight, they are at their most comfortable in the dark or dim light, most likely because their eyes don't have much natural protection from glare. So, yes, sunglasses would probably serve them well and Garak should totally have been rocking a visor.
