I wonder how much correlation this has with exercise. Generally if you are getting good levels of sunlight, there is a good chance you are outside exercising, even if it's just walking.
After all, exercise is the undisputed God tier all-time winning champion of "Studies show that ______ is good for xyz."
I've taken up running because it's a way to get sunlight during the winter, I can run in shorts and a t shirt. I am very active, but I start getting a lot of anxiety if I don't get sunlight on my skin for a week or two.
I remember a study where they shone light on the back of the knee to control for this.
While I believe there are many benefits of being outside and exercising, there does appear to be specific benefits to sun-like UV exposure.
Also gives you a brief respite from sitting in a climate-controlled environment and staring at screens.