Why does it make a difference?

I was coming to post about something else but an email I've found on the way has changed the topic!
So.
This email was from a friend and it was a forward from a friend of theirs regarding blood/bone marrow donation as a general need and specifically for their daughter (the friend of a friend's daughter. Keeping up?!) I am not a blood donor because I can't be - I had two blood transfusions (following my two jaw operations) in the "bad" window when bloods were not properly screened and there was BSE and so on. So I can't donate blood now or ever. That's a slight tangent.
With this email was a flyer highlighting the family's campaign. I was thinking along the lines of "oh, that's sad, poor them, hope it works out" before opening the flyer. Then I opened it and the girl affected is just gorgeous. About eight years old, beautiful smile, really bright looking, her hair in cute bunches and so on. So now the story is devastating, desperately sad, wish I could donate (but see above, I can't - though maybe bone marrow? I don't know.)
Why does the fact that she is cute make any difference at all? Obviously there have been studies into things like maternal instincts and that cuter children (bigger eyes, whatever it is) do bring out more of the natural desire to protect but still...
I can't ever know if the reaction would have been the same on opening the flyer - maybe it was just having a face to the problem that was the trigger and how she looked didn't really have anything to do with it but I think we've probably seen this on bigger scales anyway to know that it isn't just me and that the story and just a face does not produce the same interest as a story and a pretty face. Thoughts?