Well I don’t think he actually mentioned lacking skills. I won’t try to put words in the OP’s mouth, but I think for some people it is a mental thing. The eldest of my two sisters would be a good example of this. She purchased a scooter for herself with the intent of riding it downtown. She thought she would save gas and parking by commuting in what she thought would be a fun and fuel efficient way. As it turns out, the first time she took it outside her neighborhood and into traffic it terrified her. Now she takes it only around the neighborhood. She still says it scares her. Here is a case of someone who probably shouldn’t be riding.
Just read a forum post over the weekend. I can’t recall if it was here or elsewhere since I read a few. The poster purchased a used bike with almost no miles on it. Apparently the original purchaser bought the thing, rode it home, decided it wasn’t for her, and garaged it until the new buyer purchased it. Another case of someone who probably shouldn’t be riding and realized it.