Ok this is my first post. I don't know if it'll get any attention but I don't know where else to put this to ask.

To preface, my mom is an alcoholic. She drank a lot at work and around me as a kid. She'd practically pride herself on her skills in being able to work and drive while drinking. She'd lie about how much she drank and from the age of 2 I got into the habit of checking around the house for bottles, smelling water left out before drinking it, being hypervigilant when observing my mom for any signs she was drunk.

So my situation/question is my boyfriend (27) is a roofer and in the last couple years he's advanced his career, taken on more responsibilities, worked his body more, gotten older... and in turn he's started to drink more. Not in excess or anything but now he comes home with an already open can of beer. If I get upset or ask about why he's drinking on the clock, he tells me his coworkers do it, his boss has been for years, the house he just did a repair on still had a beer in the gutter from the previous roofer, "its normal babe". But I just don't understand how drinking at work can be... fine?? He tells me it's just "a beer" or it's just "a couple beers", "I'd pass a breathalyzer if pulled over, it's not a big deal". And I don't think it's asking too much for him to just wait till he's off the clock to crack open a beer, or wait till the home owner offers him one for a hard days work. But he depicts a story and field where that is not the norm and I'm asking him to do something that would confirm this mole hill is a mountain when that's not the case for him, it's just a little hill.

To be clear, he is a great boyfriend and doesn't ever do things (especially if I express it) to upset me. Hes very loving, caring, attentive, and we dont really argue aside from this one topic. So I don't think he's trying to upset me, he's just tryna get through his work day. But I can't wrap my head around this being a "normal" thing in the blue collar field. Can someone give me a 2nd opinion or advice on this? Am I the asshole for expecting him to not have a beer at work?