Because for us women it means a lot more to us that a man would choose us, preferably a man that we like. If we choose him then that sets the tone for the rest of the relationship. I know I will have to be responsible to set up dates and be in charge and do everything like if I am the man just because the guy put no effort into approaching me. I've been through this more than once and it is tested to be accurate. If the guy doesn't approach then he just isn't that into you. I think it's more of a society thing rather than instinctual. I mean maybe back in caveman days it was probably instinctual, but now we are more evolved, yet we still act this way due to social issues.
Girls are subtle because they are insecure. They don't want to deal with the awkwardness that goes with the rejection. If you like a girl that is being subtle, start making some moves on her, ones that aren't too extreme, but show you like her. Give her attention, or flirt with her. That will give her confidence to be more outgoing. Sometimes girls react to a challenge as well, but that has a tendency to point the girl in the other direction. It all depends on the girl. Also she is being subtle because she is unsure about your opinions. If you make them more clear, then she will make them more clear herself.
I am insecure and shy and have too much pride to let someone know I like them so I play it subtle until I know their interest for sure. I don't want to put myself on the line... rejection sucks and I can take it but rejection in the moment is tough, when the guy is right in front of you, that's the intimidating part.
It is just the way us women are. We don't want to be rejected by the guy we like. The best thing to do is play it cool and wait until the guy makes the first move. Don't ever wait for a girl to come up forward and say she likes you, unless she has received some signals from you.
it's easy to say who cares if they get rejected, but when it comes down to it, it's not an easy thing to accept. and clearly you know that since you don't want to be rejected by girls. if you weren't afraid of it, then you wouldn't be wishing girls would do more