Let me disprove the folowing statement for anyone in doubt.
It could be said that no human being cares about anyone tub themselves.
Why would anyone serve in any of the armed forces then? What about those that gave their lives in numorus wars to save their countrys?
What about a family that used to rent from us? There was a family of 3: Dad, Mom, Kid. The dad's crazy brother was staying at thier house. One day, brother desides that he is going to kill mom and kid. Dad jumps in front of brother with gun and dies, giving his wife and child a chance to live. They did. By the way, crazy brother acctually listens to the light bulbs. No joke. Mental hospital for life.
What about Jesus Christ? Even if you don't belive that he is the Son of God, there is historical proof that he did die on a cross and did belive he was dieing for others. If you do belive that he was the Son of God, then you understand why he died.