It is informal speech. Some people choose to use informal speech in work environments. Others believe it to be inappropriate. I'm in the latter camp but I don't push my language preferences on others - just as I don't push my coding style. So now you've met two people, but in reality you probably are familiar with many more who are silent.
i usually say 'darn' just to be safe, unless/until everyone knows each other, etc.
and i'm still surprised when an interviewer drops an S-bomb or F-bomb or whatever.
when i moved from north (US of A) to the south, back in the day, some religious folks would cuss by saying things like 'Dah-gommit' and things like that.
