@Rubix - severe overcooking may decrease the vitamin content of foods but not necessarily completely remove it. This fact, rather amazingly - that cooking can degrade the vitamin content of food - was taken into account by the medical scientists who devised the RDA schedules in the first place - but thats not what you said.
You commented on JohnKs post that "a varied diet of fruit, veg meat and fish contained all the vitamins you needed" was "mainly untrue", which most certainly is not "mainly untrue". All your other comments regarding GM drops, pesticide and low bioavailability are purely your unsubstantiated supposition and speculation, when applied to your typical Northern Hemisphere foods.
If someone wants to squander their money on vitamin supplements, fine,thats their choice, but don't try to assert that such supplements are either necessary or essential for the overwhelming majority of the population that are following a basic,varied diet.
To be frank, even a pretty rubbish junk food diet will contain a very large proportion of your needed daily requirements - The Internationally recommended daily amounts are usually deliberately overstated.
Only certain subgroups, such as the elderly, those with severe dietary challenges, kids etc should ever need any form of vitamin supplementation. Vitamin D for those living in the Northern Hemisphere may be a special case, and there is some interesting research going on which may result in an increase in the RDA ,but thats a different area.