The dirty secret is we purposely recruit people in poor and desperate economic and cultural situations. They are easier to convince, they work cheaper, and fewer people will miss them if they die. Sure, it's brutal, but this is war people and this is how it's always been. Recruiters go specifically to these types of neighborhoods and show them pictures of exotic places all throughout the world that they 'might' see and give them details on how short their tour will be and how unlikely it is they will be stationed in Iraq... and then boom! Their parents are getting a letter that the US's gamble with their child's life didn't go as planned. Sorry for your loss.
Except this is not really how it's always been - in the U.S. at least. We used to have a draft and therefore had young people from all socio-economic levels in the military. (Sure, some people gamed the system but it was still more fair than it is now.)