A lot of industries are going to look really bad if you only score one side of the ledger.

Absolutely. However.

Given that a huge number of people continue to smoke

While that's obviously true...

and enjoy it,

...I think that's misleading. While smokers like and presumably enjoy the relief cigarettes provide from cravings, I doubt that at reflective equilibrium they'd want to be smokers, or would approve of their smoking. When samples of smokers in Canada, the US, the UK, and Australia were surveyed, about 90% agreed with the proposition that if they could live their lives again they would not start smoking, and a clear majority (67% to 82%, depending on the country) reported an intention to quit within the next year. In Gallup polls, most US smokers say they believe they're addicted to cigarettes, and most say they'd like to give up the habit. The CDC reports that in 2010, 43% of US adults who usually smoked cigarettes daily actually did stop smoking for multiple days because they were trying to quit.

despite knowing the negative implications for their health

Not true in general. Another paper based on data from that four-country survey tells us that "[a]bout 10% or more of smokers did not believe that smoking causes heart disease. Over 20% and 40% did not believe smoking causes stroke and impotence, respectively."

it seems reasonable to assume that tobacco companies supply the world with a great deal of utility, in addition to the lung cancer.

I remain extremely sceptical, not only because of the evidence I summarize above, but also because of economic, philosophical & cognitive considerations of the sort LW likes:

• Tobacco manufacturers, in effect, value a life at ~$10k. This is far less than other estimates of the monetary value of a life, at least in developed countries. Is everybody else effectively over-valuing lives, or are tobacco companies effectively under-valuing them?

• I can apply the reversal test by asking myself whether humanity would be better off if many more people smoked. Or: would humanity be worse off if cigarettes had never been invented? Or: if cigarettes had only just been invented, would it be a good idea to subsidize their production & distribution to get them into the public's hands faster? Intuitively, a "yes" answer to these questions seems strange to me.

• Cognitive bias is ubiquitous, and people's preferences over time are often muddles that don't cohere. In light of this, the fact that many people use/enjoy something isn't proof that it gives them positive net utility; and when that something dispenses an addictive chemical, it's weaker evidence still. Various cues can trigger a craving for a cigarette, which is why people giving advice on quitting smoking routinely recommend avoiding cues that engender desires to smoke; that advice would not be necessary if people decided to light up on the basis of level-headed ratiocination.

All in all, there is a lot of evidence that revealed preference theory gives us the wrong answer when applied to smoking. Most smokers say they regret taking up the habit, are addicted to it, would like to quit, or intend to quit; many have already tried to quit; many smokers cannot identify all of smoking's potential health implications; applying revealed preference theory to tobacco manufacturers instead of smokers suggests manufacturers value customers' lives suspiciously cheaply; calling on intuition by imagining counterfactual scenarios suggests that cigarettes aren't a boon to humanity; and people's actions are known to correlate imperfectly with their goals, and indeed their desires & decisions to smoke are influenced by sensory cues which would not enter into a rational cost-benefit calculation.

The most parsimonious explanation of these observations, in my judgement, is the mainstream one: the downsides of cigarettes massively outweigh the upsides; people typically begin to smoke cigarettes because of a temporary failure to adequately weigh costs against benefits; and people continue smoking because they become addicted to nicotine, and condition themselves to associate the paraphernalia & physical motions of smoking with nicotine self-administration.