"I've never heard more different explanations for anything parents tell kids than why they shouldn't swear. Every parent I know forbids their children to swear, and yet no two of them have the same justification. It's clear most start with not wanting kids to swear, then make up the reason afterward.
So my theory about what's going on is that the function of swearwords is to mark the speaker as an adult. There's no difference in the meaning of "shit" and "poopoo." So why should one be ok for kids to say and one forbidden? The only explanation is: by definition."
So swear words are both: Restricted to adults only. Unprofessional.
I would think a likely explanation is: they are emotionally charged. They signal danger. You are not allowed to have dangerous emotions while being a non-adult (lack of self-restraint) or while being a professional (can affect sales or internal relationships).