Hi Highway1980,
That is a doozy of a question. I don't know the real answer - or answers. I do have a couple of ideas. This is a beast that I did battle with not long back, so I hope you also don't mine my own story.
One is strictly syllogistic. A negative statement is logically impossible to prove.
If someone says "AmeriKaur, prove that you went to your martial arts class today," that is a easier than proving that I didn't go.
The other opinion is in the way of Sikhism itself.
The vagueness that you speak of is absolutely true. Sihkism is not a dogmatic religion.
The Gurus instead took a more introspective approach. They wanted us to look inside ourselves. They wanted us to look to God. So much emphasis is placed on Simran. Why is this done? For spiritual reasons, it is a way to get closer to God.
For practical reasons, it is a way for the individual Sikh to find the true path, and get our questions answered...not just answered, but answered in a way that makes sense.
But such conflicts have come up before. Enter the need for the rehat maryada or Sikh Code of Conduct. The rehat maryada is about 100 years old and was written by humans, that agreed upon what behavior was acceptable and what behavior wasn't acceptable. This is where one will find verbage that is more dogmatic, such as to specifically not drink, not smoke, or not do drugs. The Rehat's own rules state that following the Rehat is encouraged for a non-Amritdhari Sikh, mandatory for an Amritdhari Sikh.
But the Rehat Maryada is controversial. Some accept all of it or mosto of it and follow it. Some reject it. Some Sikhs doubt it's need or authority, as it is not gurbani.
But, there are problems even with dogmatism...as one can use or twist dogmatism to suit a given agenda. Think of Bill Clinton saying that a certain kind of sex is not a sin, because it is not forbidden in the Bible. Even dogmatism has it's limits.
So, do I think that many Sikhs drink because of the vagueness in Gurbani?
Maybe some.
Some of it also has to do with self-discipline, self-restraint, and the fact that social drinking tends to begat social drinking.
For me, I used to drink socially, I grew up in a non-Sikh family where both of my parents drank lightly. By lightly I mean, never everyday and never more than two glasses of wine. I copied my parents there.
I was surprised, and a little frustrated, at how hard alcohol was to give up. It was the social part of it...it's what I do when I go out with friends. Have dinner, and a drink. And my friends like to have dinner, and a drink. Some of my friends even said "Don't give it up entirely, it relaxes you, you know"
I'm embarassed to say that it took me a long, long, long time (a few years) to finally cut myself away and say that I honestly "don't drink." I asked God for help "God, please make me hate this stuff."
I focused on finding more friends that don't drink, to help build a new lifestyle...and this was key, because this gave me the strength I needed to be around my old friends that still have a glass of wine or two...and not feel like I have to indulge in the drink to enjoy their company. My buddies in martial arts helped me more than they will ever know.
developing self-discipline, developing self-restraint, dogmatic scriptures, personal desirs, social patterns...I honestly don't know what the magic "off" switch was that would get Sikhs to stop drinking en masse.
Maybe, each individual Sikh has to find their own way, in a way that makes sense to them.
That is only my opinion though. What do you think?