In the PT, all of the emotional catalysts are things that normal people can't relate to. Most people can't relate to being super-powerful and chosen to "bring balance" to anything. Most people can't relate to being a senator, and can't sympathise with all of Padme's day-to-day problems.
Luke on the other hand, is just an ordinary kid who dreams of doing something great. It is something people can relate to better. Everyone wants to be the hero, to get the girl--if you don't know that she's your sister. Being stuck at home with a mundane life is something that kids and adults alike can relate to. But most of us can't relate to being separated from our mothers and then finding her dying, tortured by nomads.
So it is really lack of humanity, but lack of normal people.