I took a gap year when I was 35 and travelled with everything I needed in a backpack. I didn't miss any of my possessions, or feel like I needed anything else. When I returned home, I felt quite horrified at how much stuff I had. Clothes that weren't worn much, kitchenalia, ornamental stuff. I sold a lot of things because I felt I didn't need them, and I was looking to downsize anyway.
Now, I realise that I got sucked back in to 'posessions' and my stuff has grown / filled the house again. Some of it is valued and worthwhile; it brings me joy. Some of what I own is just unnecessary though.
I also lost everything in a flood six years ago. A lot of sentimental stuff. Again, things have grown and filled all the cupboards and wardrobe space. Some of that is down to having a child, and their needs, some of it, again, is probably unnecessary.
I'm currently battling to have a clear out, as having too much stuff stresses me out.
Regarding cars, I keep mine until they break. My best friend, however, buys a new car and is then immediately fancying a new one. Less than a year later she will trade in. She knows she loses lots of money doing this, and accepts that her savings is depleted as a result. She even says she could probably have paid her mortgage off if she didn't keep changing cars.
A lot of it is possibly down to boredom. Some people, I think feel the need to have the latest of everything, and it can become a viscous circle of greed and debt. Shopping addiction is definitely a thing among some people I know. Trying to find something to make them happy and get the constant dopamine hits. ADHD is an example of this type of behaviour.
For transparency, I have Autism and ADHD. The Autistic person in me wants calm, order and tidiness. The ADHD side quite often wants the shiny new things and the excitement of parcels being delivered.