There is the famous Yes, Minister argument about smokers being a net postitive for the NHS given that they are likely to die younger of smoking related diseases instead of requiring expensive care for more complex diseases later in life.
A study in Finland found that each smoker contributed a net positive of 133,000 euros to their health system by dying younger (on average). Source: https://pubmed.ncbi.nlm.nih.gov/23233699/
I don't think people in the UK care about this though. People seem to be consistently in favour of banning anything that they don't personally partake in. This is despite the fact that smoking rates are at their lowest levels ever and still falling.
Labour are looking for a policy which is cheap for them to implement but has some popular support so they can basically say, "look at us; we're governing!"