Herp. Yes, living causes cancer as eventually a cell replication will go wrong. However, carcinogens - like asbestos or tobacco smoke - cause cancer much faster and might also result in a more aggressive growth than "naturally" occurring cancer. Now, carcinogens have a wide range of lethality, as do the different types of cancer, which is often ignored by the sensationalist media, because "OMG THIS KILLZ" and "OMG THIS MAEK YOU LIVE LIEK 4EVA!" sell much better.
Say, one in five smokers gets lung cancer (those who escaped it have still a WTFHUEG risk of getting another cancer compared to nonsmokers), if you are not subjected to tobacco smoke or asbestos the risk of lung cancer is almost nil (statistics that show non-smokers getting lung cancer do not differentiate "passive smokers"). Then, some obscure food additive might increase your chance of getting some really rare cancer according to a research paper, but if the risk increases from 15 in 100,000 to 16 in 100,000, the cause and effect are not as clear anymore even if the difference was in this study statistically significant.
Then, it's also about the treatability of a cancer. Some cancers are all but curable: the five-year survival rate of breast cancer patients getting it this year (as opposed to comparing to historical survival data which might lag 10-30 years behind state of the art treatments) was recently estimated by the local university hospital to be upwards of 98%. Meanwhile, lung cancer five-year survival rate is still on the average 15%...