Why do some women give up/not approach a guy they're interested in?

I've been lurking this subreddit for sometime now and I am finding there is a trend with a lot of the posts I am seeing.

I see a lot of posts where the OP will ask "Is he interested in me?" or "how to know if a guy likes you?". I've also seen a lot of redditors will often say "just ask him". Sometimes I will also see questions like "why won't guys approach me" and similar.

Yesterday I saw a question asking if things were over with a guy because her friend came over and she assumed the interested man thought her and her friend were a couple and stopped pursuing her. Instead of talking to the guy and letting him know she was interested, the OP put out an update saying she believes the guy lost interest and now she isn't going to attempt anything.

Why is this a common occurance? Why is it hard for some women to approach men and be direct about their interest? Why is it more acceptable to come to this subreddit to deduce if a man is interested in a woman?