All cancer is genetic but not all cancer is hereditary. Essentially all cancer comes from DNA damage which changes the cell to become cancerous.

Many environmental exposures can cause this, and for some individuals they are born with a genetic trait which makes them more susceptible to cancer. At the end of the day even the healthiest person in the world has a chance of cancer and many risk factors are outside of our control. For example all women have a higher risk for breast cancer (~11%) simply because they have more breast tissue than men. Then your risk is further influenced by other things like age of menstrual period, if you ever gave birth, if you have naturally dense or fibrous breasts, etc etc.

Like the other commenter said, if you have no family history that’s definitely a good thing, but nobody has “nothing to worry about” when it comes to cancer. That’s why regardless of family history or lifestyle, If you’re a woman you need to get annual breast exams when you reach a certain age, all men need prostate screening eventually, and everyone needs a colonoscopy eventually. These are all screenings for common cancers which can occur in anyone.