You will get all the vitamins you need just from eating a balanced diet.” Oh yeah? Consider Vitamin E as an example. While cheerfully admitting that fresh olive oil contains natural beneficial cofactors, count the number of IU's of vitamin E in it. There are 26 mg of vitamin E in a CUP of olive oil. (A milligram is close to an IU.) The amount of E that is preventive of cardiovascular disease is at least 100 IU, probably 400 IU, possibly as much as 800 IU daily. And a CUP of olive oil contains less than 30 IU.
You simply cannot (and should not) eat a sufficiently large quantity of oil to get ample vitamin E. It is very difficult indeed to achieve even the lowly US RDA's of many important nutrients from your foods alone...unless you eat many portions... in which case you get fat!