Well, there are a few intentional reasons:

• Eugenics - there are many people whole thing we have way, way, way too many people on the planet. They believe in order to save humanity, birth controls need to be put in place - failing that, creating scenarios where people kill themselves is good too (look into black-on-black crime, for example).
  
• Hubris and Fun - Most of the people who run the planet came from a family line of others who run the planet... well, the finances of the planet. So, in their perspective, they believe they can do whatever they want to their subjects (you and me). In the same way a sociopathic child might harm animals for fun; these grown sociopaths have the world population with which to play.
  
• Headless Gov't Projects - some senator may have had the ability to build a budget and needed to spend money on SOMEthing, so with eugenics loosely in mind, created some program. With the gov't being so large, that senator moved on and now that nonsense project which hurts or kills people now lives on - with no one driving it anymore.
  

I would guess the biggest efforts come from eugenics though - that is a philosophy you see throughout all of the Bilderbergers, for example. Look at Bill Gates - undrinkable water would be significantly easier and cheaper to fix (in fact that is now a solved problem).

Clean water would be a simple way to cure disease in 3rd-world countries. Instead, he is for vaccinating children against the diseases they got in the dirty drinking water. Far more children die this way both from the disease and from reactions to the vaccines because of their overworked immune systems.

In fact, Bill Gates did a Ted Talk on his eugenics utopia.