If the 15 things were meant to keep you alive in a wilderness area for a couple of months then I'd find the whole thing a lot more interesting - living "minimally" in an urban environment with a healthy bank balance doesn't seem that much of a challenge.
I don't think people are after "a challenge" with this minimalist urban life style.
It just feels good to be free of stuff. At least for me it was one of the greatest periods of my life. Around 10 years ago, after a breakup with a girl I was living with, I got rid of most of my stuff, mainly kept a few clothes and things that I couldn't replace somehow like letters from my friends and photographs. But furniture, utensils, books, CDs, vinyls, all that I sold to thrift stores.
The feeling was awesome, being free from stuff and relationship. There was nothing challenging living that way. Only challenge was a decision to get rid of stuff (and her).
I would agree that there isn't much point having stuff that you don't use - but I like having stuff that lets me do activities easily when I want to (bike, skis, assorted mountain gear...). I don't feel a huge amount of attachment to these items as possessions - only for what they let me do.
