Why you should never risk your life for a female that's a stranger.

I know a lot of you are either going to say "it's just a movie", or "you're not a real man", but hear me out. Most women won't react or care enough to help a stranger that's risked their lives for them. When the neighbor in this movie got stabbed and had the killer in a headlock, which basically incapacitated him for the time being, what did the lead girl do? She just sat down like an assh*le watching and thinking about herself. Now if the killer was on top of the neighbor stabbing him I'd understand that reaction, and yes I know this is a movie, but after seeing tons of white knights get their ass kicked in real life protecting "random girls" who just stand besides them looking shocked this is how I assume most females will react. Of course there are some tough chicks that probably will help out, but let's be honest, the majority wont.
Why risk your life for someone who doesn't care about you, or won't reciprocate the same actions if you were in their position?
Now if the female was your wife, or a family member, that's a completely different story. But I'd rather live and not be considered a "man", by idiots who would die to prove how tough they are, than die risking my life for someone who wouldn't help me out in the same situation.