There is a component of elitism here. If you're poor, you hang on to stuff, because it may come in handy. If you have enough money and some left over, you can get rid of stuff, because if it turns out you really needed one of the things you got rid of, you can buy a new one. But if you can't afford the new one, you keep stuff "just in case".
But, even if minimalism may require a certain level of financial not-on-the-edge, for many of us, it's not a pose. For myself, I just hate clutter. As Paul Graham said, a cluttered scene takes more mental energy to parse. If there's enough clutter that you have to move around stuff, it takes more physical energy just to walk across the room. I don't have time in my life for that kind of waste.