Do ppl really stop at 1 glass?

My bf has recently started drinking in name of peer pressure and says he just takes 1 glass so ppl wont keep bothering him throughout. And says if he doesn’t they wont include him in their plans. I myself have never touched alcohol..What to do..i have a lil problem with it but still can accept him drinking a glass n not getting drunk..but do ppl really stop at one? N how high are the chances its gonna increase in future? Pls help!