Why do you take vitamins?

An article came out about a week ago, saying certan vitamins don't reduce a list of diseases including prostate, colorectal, lung, bladder or pancreatic cancer.

The group of vitamins include C, E and selenium.

Hmmm...I know for years, vitamins were thought to have some benefit (I take one every day) but to help reduce the risk of some cancers? That seems like a pretty tall order. I was wondering, if you take vitamins, why? Do you think they can reduce the risk of some chronic conditions? Is it a supplement to a healthy diet? Do you skip them altogether?