Getting an emotional response to NPCs from PCs.

How does one get characters to actually care about NPCs? I have been struggling with this for some time in my current groups. I think it must be one of my faults as a GM. It isn't that I try to force an emotional attachment to any particular NPC, the problem is that they don't seem to care about any of them. It doesn't matter if they are a good, bad or neutral character in the game. They kill the bad guys but it feels like they don't respond to it. The other NPCs in the game, they couldn't care less.

I have tried many different ways to try to get PCs buy-in on NPCs. I have tried getting them to making NPCs they care about on notecards before the game as in my current L5R game. I have tried the long game where the NPCs are around for several sessions helping the PCs and then get in trouble asking the players for help. I have read blogs all over trying to figure out if there is anything I could be doing better. I have tried several different suggestions. Therefore, I am going to try my blog. I know I haven't posted in a while, I am not going to make an excuse, but I am going to try to post more.

If anyone has any ideas, please post them as I could use some help.