The same way your fingers are "not designed" for computer keyboards, your hands for steering wheel etc.
No one is in a position to make pronouncements on what the chief programmer of the universe had in mind, or what it is that he is trying to do. In practice, whatever works, goes.
Regarding the alleged harmfulness of tobacco smoke, like most people you have been duped by the mercenary pseudo-science, bought and promoted largely by the pharmaceutical industry, which is also the chief creator and sponsor of the "grass roots" antismoking groups, buyer of antismoking laws and regulations, etc.
While the pharma uses FDA, CDC, politicians & bureaucrats to muscle out many medicinal plants and natural remedies, their most fierce and persistent attacks are aimed at the best one of them all, the ancient medicinal plant tobacco used by billions of humans for the last 8000 years.
There was a long thread "Smoking is good for you" on, of all places, the leading life extension and nootropic forum "Longecity". After months of debate, countless papers and references brought up and discussed, there was no contest -- the antismoking side, which was nearly everyone there initially, had nothing but junk science on their side (correlations on non-randomized samples), while all the hard science (experiments, randomized trials) was on my side (I post as "nightlight" there). The "debate" was so one sided that some of these health and longevity obsessed folks started smoking as result of the facts presented.
Here are few links to the highlights of that "Smoking is good for you" thread.
1. Dogs exposed to radon or radon+smoke:
5% of smoking dogs and 37% of non-smoking dogs got lung cancers.
2. Massive National Cancer Institute sponsored experiments that
backfired terribly, setting back the NCI's workplace
smoking bans agenda for more than a decade.
3. The crowning experiments (2004, 2005) of six decades of
antismoking "science", the pinnacle -- again backfired badly,
as they always do -- at the end, more than twice as many smoking
animals alive than non-smoking ones.
4. Self-medication with tobacco
5. Common genes for lung cancer & smoking
(Fisher suspected this to be the case in 1950s, he also suggested
self-medication possibility, see page 163, where he compares taking
cigarettes away from some poor chap to taking the walking stick
from a blind man.)
http://www.york.ac.u...tat/smoking.htm
http://www.york.ac.u...t/fisher274.pdf
6. Hazards of quitting (triggers lung cancers in animal experiments)
7. Emphysema/COPD - smoking protective rather than cause
8. How does antismoking "science" lie with stats (how to "prove"
that -- Prozac causes depression -- using the master method
of antismoking "science")
9. Heart attacks from SHS myths (a 'friend saying Boo' is more
"hazardous" for your heart than SHS)
10. Glycotoxins/AGE in tobacco smoke -- backfires badly
11. Smoking protects against cancers (reversal of values in cancer state
and another common sleight of hand), Smoking vs Caloric Restrictions
(and on fundamental wrong-headedness of CR)
12. More on anti-carcinogenicity of tobacco smoke and how to translate
Orwellian antismoking "science" to real science
13. ** why take a chance
14. Smoking and diabetes, insulin sensitivity -- another "proof" backfires
15. How to prove that 'Lifting weights is harmful for muscles' -
pinhole vision sleight of hand of antismoking "science" illustrated
16. Oxidative stress, breast cancer, "randomizing non-randomized variables" sleight of hand --
more antismoking junk science claims turned upside-down by facts of hard science
17. Can one replicate the health benefits of tobacco smoke (the short list given) using supplements and pharmaceuticals?
Even if it were possible, can one do it for < $1 day
(cost for a pack of roll-your-own cigarettes with natural,
additive free tobacco)?
18. Who knows more about biochemistry of life and its molecular engineering -- one little cell in your little toe or all the
biochemists and molecular biologists in the world taken together? Is "Sickness Industry" good for your health?
You can try to make your case. I don’t need any more proof than my own eyes.