It's the difference between a tolerant atmosphere vs a welcoming one. A simple example is that when i'm with mixed company, I speak in English even if everyone i'm currently talking to can speak another language that i'm familiar with. This allows others to listen in and maybe join in the conversation. This is tossed out of the window when i'm speaking to the same folks but in private. Being welcoming means taking the extra step to make others comfortable, even if it means you end up inconveniencing yourself. Having no alcohol is more "welcoming" as it takes into account folks who might be recovering from alcoholism, while inconveniencing folks who casually drink.