What would mankind have to do if there was no hardship in the world? We'd live on this flawless paradise of a planet with nothing to do or prove, and just stagnate forever.
Throw a little strife into the mix and all of a sudden you have people who rise above and people who resort to evil, seperating the worthy from the not.
As Joe Rogan says, we're all just a consciousness piloting a sack of meat around.
The vessel isn't the important part at all. Whether its sick kids or suicide bombers, what happens to your body doesn't really matter. Its what you actually do while you're here that counts.