Indifferent is not the right word, but they're looking to see if there's a reasonable chance whether an investigation could result in a conviction and that's far from just rapes. I've had my car vandalized at night, no witnesses and really just reported it for the insurance claim. I've had a pair of brand new shoes stolen at the gym, no cameras pointing in that direction, I just reported it for the statistics so they know how much crime is really going on.
They come into the police station thinking now I'm going to get him caught and punished, but what they often end up hearing is essentially "So you were raped and from what you're telling me he's going to get away with it" and that really hurts. The standard of evidence often feels unreasonable, like what do you expect a written confession or a video recording? That's the flip side to the justice system, if you know you've been the victim of a crime but the perpetrator gets away with it the illusion that the law will protect you shatters.
Which is not to say that the gun nuts are right, it wouldn't have stopped my car from being vandalized or my shoes stolen and if she wasn't in any condition to put up a fight she wouldn't have been able to get hold of and fire a gun either. What you're really experiencing is that bad men will be able to do bad things to you and there's really no sane way of making 100% sure it doesn't. The justice system makes a difference, but it won't make things right and fair. And I'm pretty sure heaven and hell is a fairy tale for adults.