I agree that they are unprofessional. As far as I can determine, some people feel that they make a project or community seem more inclusive or welcoming - goals which I definitely consider worthwhile. But I don't personally feel that they are helpful in this persuit. Who are you trying to be inclusive of, seven year olds?
Outside of your friend group, most of us have been using smileys and emoticons in day-to-day chat for years - the presence of rich emoticons used to set messenger platforms aside from each other - and emojis are simply the latest generation of that. They’re primarily useful for providing some emotional context to some text - and whether displaying emotion is professional or not is really down to personal preference.
Maybe I'm just a robot, but by and large I don't believe that log or commit messages require emotional context. (I do use emoji for some messaging, Slack specifically.)
