Health insurers want to increase, or at least maintain, their profits. They won't deny claims because they want a better society, they want to minimize their financial risk.
So yes, one would expect to be in their commercial interest to deny cancer claims to people who willingly put themselves at excessive risk of cancer at some point in the future. It's the infinite wisdom of the free market!
Quitting alcohol is nowhere as easy as getting covid vaccines. If there was a cheap/free safe vaccine that reduced the chances of getting hospitalized or dying of cancer by >60%, your point would be more valid.
They are clearly not the same, but you first have to make the claim that insurance coverage should be tied to ease of prevention at all, before arguing where the line should be.
I'm not aware of any other risky behaviors that exclude coverage, so this would be a precedent.
If you don't have 3-4 comordibities your risk of hospitalization + dying of COVID is so low it's close to zero. Not sure what you point is, unless you consider everyone has loads of comorbidities out there.
> Quitting alcohol is nowhere as easy as getting covid vaccines
you have a choice to buy the next bottle or not, as far as I know. It's not like addiction is unavoidable. And cancer risk for alcohol consumption is not even related to addiction, you increase your risk of cancer significantly even with a small, non-zero consumption of alcohol. Look at the data.
Will health insurers deny claims related to cancer if you have been drinking alcohol? Good luck living in that world.