I would add that it helps people not just to think about things adding value, but also add costs. It's the old Fight Club adage about "the things you own, own you", and "only when you have nothing, can you do anything."
While it can be taken to the extreme, the underlying premise is true. Buy a new car and you're going to be worried about taking care of it. Buy a used car and you're a bit less worried b/c it already has some scratches. Don't buy a car at all, and you're never worried about the car (maybe how to get places if you don't live in a city...)
The goal should be to only add things to your life where the value is more than the costs. One situation where people have huge differing opinions is kids. Kids probably cost more than anything else someone can obtain in life. They are expensive money wise, time wise, and emotionally, but for some the value is huge, and others not so much.
>Minimalism is a lifestyle that helps people question what things add value to their lives.
The movement involves reflecting on your personal values, so of course it's going to have almost as many expressions as there are people doing it.