I think you are attributing way too much significance to the power of Vitamin D.
Ummm seriously? Just do a simple google search of inflammatory disease and Vitamin D.
You still need sun to activate the pills.
Your kids might be out but for most that's only a recent occurrence. Most kids spend at least a few min outside each day, even in wintertime. For about a month many kids in the city did not do that at all. Even for a few minutes a day. Do we know the effect of spending 10 min a day outside vs 0? I know it might seem like a small amount, but it's very possible that that's enough to keep us going and when we don't get that, certain things start failing.