I don't believe a colonoscopy is a random test. Many people could have problems without being aware of it and only been discovered when the test is done. Do you have a mammogram every year? A pap smear? I know these test are a lot less invasive, but only when someone is diagnosed with colon cancer do they wish they had the test done before it was too late. Is done every 5 or 10 years because many colon cancers grow slowly. If you search around the internet you will find tons of information and opinions on why not to do it, but even much more on why is it beneficial to you. It could save your life.