The concept itself....
This is an interesting documentary, which does make one reflect on our expectations from life, and how we see ourselves.
Mainly, it makes me think, Okay, if you strip away your conventional home and its payments and responsibilities (and all the possessions that go in it), and you are left with yourself in a tiny house....what do you then do with your life? Your costs have gone way down, so you would work less...and what then does it mean you would do with your life? What will you do with your days, now that they are not tethered to paying off a house, rent, etc.
Many people make their lives about their children and family...but I don't see raising a child (or god forbid, children!) in a tiny space like this. And you had better REALLY get along with and want to get enmeshed with your partner if you're going to share such a (tiny) living space!
I suppose this type of house would appeal to someone who wanted "freedom"....but then it leads each person to answer, "The freedom to do WHAT?" And you will be doing it without shelves and shelves of books, or a china collection, or wardrobes of beloved clothes/jewelry/shoes, if that's your style. EVERYTHING will get smaller. One is essentially getting naked.
In this sense, the concept is confrontational, with one's self.