Vegan diets are a slightly special situation. If you're vegan you at least need to supplement B12 and you might be more likely to be deficient in other vitamins as well compared to non-vegans, regardless of whether they are consuming processed foods that are fortified with vitamins.

I think when people are saying that vitamin supplementation isn't necessary in general, they are not talking about vegans.

I wonder, though -- my own experience is my only data-point -- but I got pretty close as a lazy bachelor presumably because of the vitamins that are added to so many things.

For example: the Silk soy milk I buy includes the following ingredients: Calcium Carbonate, Vitamin A Palmitate, Vitamin D2, Riboflavin [B2], Vitamin B12. Do they juice it with extra 12 because they know dirty hippies like me aren't eating eggs? I'd believe it.

So do I really need a separate B12 supplement? Now that I'm a [just as lazy] middle-aged vegan with better access to groceries and a partner that loves to cook I really wonder.

Livestocks is also heavily supplemented, non-vegan can avoid supplements in our modern world but what they eat do eat supplement.

Hard to comment on this without knowing what you weren’t hitting in your diet. Any idea what was low?

I'm sorry but it was so long ago I've long since forgotten; I don't know that my lazy bachelorhood diet is a good example anyway (cooking for one with less emphasis on fresh vegetables and more on what I could fit in my backpack to carry home).