The problem is that is a billion people, and they aren't the only ones who live next to that river. It's the people upstream who are also defecating into the r

The problem is that is a billion people, and they aren't the only ones who live next to that river. It's the people upstream who are also defecating into the river that are likely causing them to get sick. And digging a hole in the field for the village to go in can be a bad idea because that area becomes a breeding ground for all kinds of bad stuff. This isn't like when you went camping and pooped in the bushes one time. This is millions of people, every day, for decades. The waste builds up unless it's taken care of, and putting your waste into the river where it will be washed away starts to look like a viable strategy. Maybe these people aren't as dumb as you think, they just live in a very different environment and didn't have your education.