Because it's in the same caliber of stuff that's easy for women to lie about and get people to believe. How thorough do you think an investigation into a cat-call is going to be? Realistically she'd just need to get like 1 or 2 of her friends to give false testimony.
i'm fairly certain these cases are handled better than just 'listen to the victim and their biased friends.' I'd expect there to be other witnesses, checks for physical injury or signs of struggle, and if none of that works they'll probably drop it on inconclusive evidence.
Eyewitness Identification has its issues, none of which relate to the gender of the witness. You can't just blame false accusations on women and say thats a reason why women can't be trusted