I thought I’d piggyback off Dave’s post on the Church’s latest article clarifying how vaping, green tea, and marijuana fit in to the Word of Wisdom, although none of these are mentioned in D&C 89. This clarification is likely the result of two things: 1) these specific items are mainstream now, more popular than substances in prior church statements, and 2) in the research Jana Reiss covers in The Next Mormons, LDS millenials are drinking coffee in record numbers (particularly since when I was growing up, those numbers hovered around zero).
We can’t really discuss the point of the Word of Wisdom without understanding its historical context. It was originally given in D&C 89 “not by way of commandment.” It was only required starting in 1921, and then not really enforced in the Temple Recommend interview until the mid-20th century. The phrase “hot drinks” is taken literally for members of other restoration sects who wait for their coffee to cool before drinking it. Church leaders have had strong differing opinions about Word of Wisdom-adjacent items like colas, chocolate and rum cake. 
When we ask what the point of the Word of Wisdom is, we might also ask what the point of it was vs. what it is now. They may not be the same thing at all. For example, I always wondered how some of the following factors played into the evolution of the Word of Wisdom:
- Joseph Smith’s father’s drinking habits
- The expense of tea and coffee, that were mostly imports, for early saints
- Health crazes like the Battle Creek Sanitarium (run by Kellogg, yes the cereal guy) that became all the rage in the mid-1800s
- Difficulty with meat being tainted due to lack of refrigeration and poor inspection standards
- The emergence of colas which were originally laced with highly-addictive cocaine
- Temperance movements in the US
- Prohibition and the accompanying attitudes thanks to the Roaring 20s
- The backlash against the counter-cultural movement in the 1960s
- Now, the rise of Starbucks (OK, maybe a decade or more ago, but the Church tends to operate on a lag)
So with all that in mind, what is the current main point of the Word of Wisdom? Here are some possibilities:
- Health Code. This rationale states that the Word of Wisdom is about being physically healthy so you can run and not be weary and be receptive to the Spirit. Detractors of the Word of Wisdom like to note that Mormons have many unhealthy habits that aren’t prohibited by the Word of Wisdom (sugary drinks for one, and I’ll include canned mushroom soup as a base–white sauce isn’t rocket science, people!). And I would add that tea drinking has no effect whatsoever on longevity; the longest lived people are those on the island of Okinawa, and tea is very popular there.
- Addiction Avoidance. This is specifically mentioned in the latest clarifying article from the Church. It could also be linked to the softer party line on colas which are not generally considered “addictive” because they are easy to quit drinking and don’t have serious side effects. Coffee and tea are far more addictive due to higher caffeine content, and nicotine has a well-documented history of addiction and negative side effects including birth defects, cancer, and death. While alcohol is not always addictive, when it is it carries significant negative impacts to the individual and family members. Likewise, marijuana has been shown to increase paranoia and decrease ambition. Go figure, the creators of Reefer Madness weren’t 100% wrong, although I haven’t seen anyone play the piano maniacally while half-baked.
- Tribal Cohesion. Behavior codes, particularly those that involve eating practices, have a strong link with social cohesion. Those who don’t drink are less likely to socialize with those who do (and vice-versa). Those who are vegan don’t usually go to BBQ restaurants. In ancient Israel, food prohibitions were linked to “uncleanliness” and they resulted in a strong disincentive to marry outside the faith. That still holds some sway today for church members.
- Increasing member commitment. Psychological studies show that the more Churches require of their members in terms of sacrifice, the longer-term the commitment of the members. When we give up a lot to attain something, we value it more, and we find it harder to leave it (thank you, sunk cost fallacy).
- Tradition. This one doesn’t hold up for me because we’ve re-clarified the Word of Wisdom so many times, but I’ll throw it out there. If you think this is the main reason we have a Word of Wisdom, what you are saying is that it’s due to the inability to let go of past well-documented dogmas. I think that’s a valid observation (we seldom do let go of these traditions that make us unique–we have a multi-generational sunk cost fallacy going on), but as I said, we keep “reinventing” and re-investing in the Word of Wisdom, updating what it means, so to me, that’s more than just holding on to the past.
- Other. If you think the main current reason is something else, tell us what you think that is in the comments.
Let’s take a vote. Defend your answer in the comments. I’m only giving you the ability to choose one, so pick the one you think is the main current reason.
 David O. McKay drank Coca Cola and ate rum cake. E. Uchtdorf has joked about drinking Diet Coke over the pulpit in Gen eral Conference. BYU banned the sale of caffeinated soda for years, claiming disingenuously that there was no demand for it (not sure how Carrie Jenkins answered the question about being honest in all her dealings, but maybe all PR people should get a pass on that one). Bruce R. McConkie felt that chocolate should be verboten.