what is gained by saying "I told you so"?There's a big difference between having "no sympathy" (which is what I said) and "I told you so".
"No sympathy" means indifference. The problems of people who didn't pay for fire service should be a cautionary tale, a warning to society at large. As the article said: by now, everyone should know about the city's fire policy. "After the last situation, I would hope that everybody would be well aware of the rural fire fees, this time"
"I told you so" is much different. It's "rubbing it in" at a personal level. I would never say "I told you so" to friends or to random people. I would, however, say it to my children in the appropriate situation. Pointing out consequences of bad choices helps children learn to make better choices.
I'm having a hard time differentiating
In "didn't pay $75", the people who don't pay but still expect to be covered are making a deliberate choice to freeload off the goodwill of their neighbors who are paying. How does a fire department exist if paying for it is optional? There is no 'fire department tooth fairy' that periodically delivers money to pay for salaries and equipment.
Cancer is much different. As you note, there isn't 100% certainly what causes a cancer. Lung cancer is one that can be closely linked to smoking, but even there it's not absolute. A quick search turns up a CDC web page that links 80% to 90% of the cases to smoking.[1]
In the case of cancer, interestingly enough it's once again an issue of insurance. Even when I was 20 years old and working a shitty no-benefit low paying job I still paid for my own health insurance. I was only being paid $4 per hour but I prioritized insurance highly enough to pay $100 per month for it. (Granted, that was 40 years ago, it's much harder to afford individual insurance today without some sort of subsidy or group policy).
In your hypothetical situations, did the stomach cancer or prostate cancer patient have insurance? If not, how is it once again not a freeloader problem? There's certainly no reason to say "I told you so". That appears to be a strawman you invented to avoid discussing the real issue which IMO is freeloading.
[1] https://www.cdc.gov/cancer/lung/basic_info/risk_factors.htm