Yeah, my blood work consistently shows low vitamin D, so I'm supposed to take it all the time anyway. I often wonder if the recommendations are based of correlations vs causations... but it's also a low cost issue for me.
I take a vitamin D supplement too. I think it's mostly because I had high cholesterol that caused a blockage when I was 37 and there are studies that show that heart issues are somehow linked to Vitamin D deficiency. I tend to agree that it could just be correlation and not causation, but it doesn't cost much so I figure it's worth not taking the chance.