Road life has its own challenges but there is no special reason to think it promotes alcoholism. To the contrary, I would say the job discourages heavy drinking because it disturbs shopping process for alcohol, money is tight for many, and there are heavy risks associated with drinking in the profession. I could see loneliness as possible contributor- but these days with smart phones not a big deal. Decades ago as a truck driver I used to hand write letters to people and drop them in the mail out in the hinterlands of the country, and of course hardly ever got anything back. That was loneliness!