<snip> Number one reason why, is because of obedience, nothing else really matters after that but we can all see the negative effects of these substances on our bodies.

We believe the body to be sacred and so anything that makes us lose control of or sustain damage to our bodies is against the will of God. The same goes for poor diet. A lot of people are not living the word of wisdom just because they abstain from those substances. There is an entire code of health that is involved with the revelation found in Doctrine and Covenants Section 88. It is a very interesting chapter.