In general, health insurance is not insurance but (frequently subsidized) prepaid medical coverage, exactly because it is not underwritten with respect to risk.
It's clearly the case that people who are overweight, smoke, or consume alcohol heavily should pay more for health insurance based on massively increased risk of loss.
Fortunately, other forms of insurance (e.g., homeowners, automobile) are not regulated in this uneconomical fashion.
As a practical matter medical underwriting didn't make decisions based on lifestyle, the decisions were made by way of broadly excluding pre-existing conditions. An an example, pre ACA my insurer (whimsically named "Golden Rule Insurance Co") made everything cardiovascular-related excluded from coverage due to very mild hypercholesterolemia.
It's clearly the case that people who are overweight, smoke, or consume alcohol heavily should pay more for health insurance based on massively increased risk of loss.
Fortunately, other forms of insurance (e.g., homeowners, automobile) are not regulated in this uneconomical fashion.