Earlier quoted context omitted.
Yeah except you might be deficient in some vitamin, and in that case you're screwing yourself over by not taking a multivitamin that has just 100% of the RDA's. Not everyone can afford to eat a world-class, healthy diet, and obtain all nutrients sans a multivitamin.
It is medically very difficult to be vitamin deficient. Modern food is fortified in so many ways that its now almost impossible unless you do something like eat exclusively exactly 1 food product. Even then. It's not about a healthy diet - it's about the fact that vitamins are trace components that your body holds onto what it needs and discards the rest. This is very different to the general nutritional needs of the…
The sad thing is while vitamin deficiency is actually fairly common it's often a slow process and the body can cope fairly well so it's less noticeable.