There is something inherently frightening about a man who describes himself primarily as “nice” when he’s trying to impress women. No one’s most unique and impressive quality is being nice. If that’s your perceived most impressive quality, then at best you don’t think highly of yourself.
But most of the time, men say they’re nice when complaining about being single. And so if their main confusion about being unattractive is how nice they are, it means that to them being nice is not a given; it’s a special shining quality. We have to put effort into our special shining qualities. We talk about being funny, especially generous, good at a skill, wise, etc. All of those require giving or working on something extra. If you rank “basic decency” in that category, it is frightening. Because no one is entitled to my humor, my wisdom, or my creativity. But people are entitled to common decency and kindness if they have not abused me.
So if you think you’re special for being nice to women you want to date, that means you don’t think it’s a given. You think you’re giving something special. So what happens when you invest “something special” in a relationship and get “nothing” back? Well I tend to stop giving that thing. If that thing is kindness, if that thing is not being hateful or violent, you are a volatile and terrifying human being. And that’s why women stay away from “nice guys”.