That says nothing about why they have trouble abstaining.
One element of it: teasing, judgement. Sometimes you fear those reactions to your decision so you pick the easy path and avoid that type of interaction. I know it sounds silly.
And you may also fear the broader possibilities when someone asks you why you are abstaining. Lots of people do.
I think a lot of it has to do with how you turn down a drink. I usually say, “No thanks,” or “I’m good, thanks,” and it rarely goes beyond that. When I hear people respond with, “I don’t drink,” or “I’m not drinking right now/tonight/this month,” that seems to invite discussion.
Everyone’s experiences are different though and I’m painting with a broad brush.
Otherwise - to your question, very circumstantial. Unsurprisingly, the more bro-like the setting, the higher the chance. I don’t surround myself with that environment constantly but it’s there from time to time.