When you don't have enough of anything, there are always conflicts about how to use it. People have different priorities. People who are convinced that they are right cannot be easily reasoned with, and so intimidation is resorted to.
Couple this with individual backgrounds. Poor, middle class, wealthy, and you get serious conflicts. My wife and I are both poor. But our early conflicts about how to spend money was because, she wanted to save it all. She fears living out of a shopping cart under the overpass, although she wasn't that poor. I wanted to spend the little we had making our current life more enjoyable. There was usually a compromise. Spend some, save some.
As our income increased, there were less discussions. She still won't let me buy the Porsche, but we do have a nice car.