Most non drinkers are most likely alcoholics themselves.
All or nothing.
I know one lad who lost his quite menial job because of his actions drinking on the job.
He claims he doesn't touch the stuff now, but the reason for that is that one sniff and it'll set him off down the same road again.
Or they grew up with alcoholics in the familly and saw firsthand what can happen.
Or they just don't like the nausea, hangover or loss of control (that feeling the next day when you remember doing something or saying something you wouldn't normally and feel embarrassed). I am not a Puritan - i infrequently use ahem certain other substances.