This study was done on people with "no nutritional deficiencies". Yet vitamins are intended as supplements for people with nutritional deficiencies. As such, this study doesn't really show what it appears to be showing.
Vitamin deficiency diseases are generally third-world diseases. The population of the U.S. has very little vitamin deficiency. It's not as if doctors see scurvey or rickets when they go out into the community.
When Americans do have vitamin deficiency, it's usually because of a disease, hereditary or acquired. For example, alcoholics get vitamin B deficiency.
The New England Journal of Medicine had a case of rickets a few years ago, and the patient was a mentally retarded child who ate a diet entirely of Pop-Tarts.
Here's another one http://www.nejm.org/doi/full/10.1056/NEJMicm1205540 -- from the Ukraine. "In addition to a diet poor in vitamin D and calcium, the patient had a history of biliary dyskinesia, which may have contributed to poor absorption of fat-soluble vitamins, including vitamin D."
Here's another one http://www.nejm.org/doi/full/10.1056/NEJMcp1113996 Autoimmune gastritis (pernicious anemia) is the most common cause of severe [vitamin B12] deficiency.
One major cause of vitamin deficiency is people on fad diets. The macrobiotic diet was one of the worst for that. Sometimes people couldn't follow the macrobiotic diet themselves, but they had an infant that they kept on a "strict" macrobiotic diet (by feeding them not much more than brown rice), and in a few cases the child died.
There are some stupid articles, like this one http://www.ncbi.nlm.nih.gov/pubmed/21310306 that simply measured vitamin D blood levels, without consideration of whether they actually had clinical disease that made any difference to the patient's health. (It's like finding an elevated PSA or a lung spot that will never develop into cancer.) If you don't know how to read a journal article, you might misinterpret this to mean that there was a lot of vitamin D deficiency. But I can't find any studies that show clinical vitamin deficiency in Americans without specific diseases, since America was industrialized during WWII.
Here's an article by people who do understand the complexity of the problem http://www.nejm.org/doi/full/10.1056/NEJMcp1009570 and here's what they say:
Randomized, controlled trials of vitamin D supplementation have addressed its effects on skeletal outcomes, but most of these trials involved supplementation with both vitamin D and calcium, making it impossible to separate out the effects attributable specifically to vitamin D.
I just spent half an hour trying to find an article in a peer-reviewed journal that describes vitamin deficiency in a population in the U.S. where the deficiency isn't the result of a serious disease, and I can't find one.
The only time Americans need vitamin supplements is when they're diagnosed with a specific disease that causes a specific deficiency. In that case, they should get treated with vitamins under the supervision of an MD. You have to find out the cause of the deficiency and treat it. Otherwise you could die. This isn't the kind of thing you can self-treat with Google searches.