We are bad at most things that are complex and require behavior change. Maybe our best victory in recent years has been the vilification of tobacco. It didn't get any less physically pleasurable to smoke, but the combination of political, social, economic, and medical pressure has turned the tide.
It takes a lot.
Yup. A lot of people blame environmental hazards for perceived clusters of cancer patients in neighborhoods. But behaviors are much bigger contributors to cancer risk these days. The best ways by far to avoid cancer these days are (1) don't smoke, (2) maintain a healthy BMI, (3) don't drink, and (4) eat plenty of vegetables. If you want to further reduce your risk of dying of cancer, (5) get the recommended screenings, and (6) get regular physical checkups and talk to your doctor about any new health problems.
Reducing one's cancer risk is well within the power of any person. But "People should just have more willpower" is an ineffectual public policy.
All the cool kids are back to smoking because vaping became too mainstream.
And none of these changes are permanent!
Look at the cultural attitudes towards smoking pot. Often the same cities/governments/people what were fining cigarette smoking out of existence suddenly have a hands-off attitude towards pot.
In NYC its illegal to smoke or drink in parks, but you can walk through a park reeking of pot and see cops writing tickets to the 2 kids who hid their beer too poorly.