I don't abstain from drinking out of any moral code or religious imperative. I'm not rebelling against the norm. I'm not making a statement. I abstain because I 1) hate the taste, and 2) don't want to "lose my mind" (in any sense).
Why do people drink?
Some claim they drink for the flavor, but I have a sensitive nose, so cheap beer smells like piss, wine and expensive beer smell like rotten fruit or grain, and strong liquor smells like rubbing alcohol. (Of course, there is quite a bit of truth in each of these perceptions. Wine IS rotten fruit, for example.) I have no desire to consume, for pleasure, a foul-smelling and -tasting substance. Many readers will no doubt suggest vodka in orange juice (or similar) as an exception to this, which is true -- but if the goal is the taste, why not drink plain orange juice?
Not everyone drinks for the flavor or odor. College students in particular consume large amounts of cheap booze to a) loosen up and/or b) get smashed. Getting smashed seems to involve blackouts, hangovers, casual sexual activity, occasional trips to the hospital, and a great deal of vomit. The former case, loosening up, has more appeal. Who doesn't want to have decreased anxiety and fewer social hangups? By reducing inhibitions, alcohol serves as a "social lubricant" for many folks. I could certainly benefit, right? In fact, this is the only appeal alcohol holds for me. However, this is directly related to the other problem: Sanctity of mind.
My mind is my most prized possession; without it I am nothing. I prize my ability to think clearly, quickly, accurately. My vocation and avocation depend on my thinking skills. If a professional racer would not put sugar in their gas tank, why would I put a known neurotoxin (and carcinogen besides!) in my bloodstream? What a ridiculous proposition.
Think about it another way: A computer that is once infected with a virus can never be trusted again (unless the hard disk is wiped clean.) You don't know what else the virus may have done, because you have no record of its actions. A virus may pull in more malicious software as well, a process of escalation and bootstrapping. Most importantly (for this analogy), the first action most malware takes is to disable any security software. Similarly, once I imbibe an inhibition-reducing substance such as alcohol, I am more likely to take in more. The more I have, the more I will likely have. It does not matter that my intention is "Only two drinks," if after two drinks I suddenly decide that I've changed my mind. The worst part is that memory is also affected, so I may not even know what I have done! It is like purposefully opening up ports on a firewall and running random programs from the internet. In all likelihood nothing bad will happen, but should something untoward occur, I am both responsible for the results and uninformed.
Sanity is already a precious enough commodity in this world. I intend to retain mine as long and as often as possible.