Partly but also because a possible summary of the new testament is "Love your neighbour". Some Christian charity is given out of base reasons but some is undoubtedly given out of that peculiarly Christian type of love. I take it that that's some kind of rhetorical claim which I'm failing to understand; nobody could really believe that their salvation is worth a million lives. No it's not. Sitting on a cushion isn't going to stop climate change or another war in the Gulf or any of the other horrors which lie in wait for us. Personal attainment is an admirable goal but it's solipsism of the highest order to think it's going to change the world.