Why is mooning considered offensive?

I means it’s a point of attraction* for both sexes. Though I don’t think the female gaze exists so that’s probably not applicable.

I mean I’m a guy and I wouldn’t be offended if a woman or man mooned me, I just don’t see the offense. Maybe if they had a prolapsed anus or hemorrhoids.

I guess it can be considered sexual harassment, but it’s never really used in that context. Or at least I don’t think so

*if applicable