I think technology is the enabling factor behind the tiny house movement.
Books, CDs, movies, photos, files, paperwork, videogames: all compressed down to the size of a hard drive. So many random gadgets have been replaced by a smart phone, like camera equipment, phones, flashlights, calendars, etc. Now people are ditching TVs as well and just using iPads and laptops to watch video.
There are other more subtle things as well. For example, I haven't needed to iron a shirt in years because nice shirts come out of the dryer looking perfect. So no need for an iron or ironing board.
Then there's service-economy-ification. Most of my neighbors don't mow their own lawn, none of them fix their own cars, and several don't even clean their own house. I wonder how many brew their own coffee? That's a huge amount of equipment that is no longer needed. When I lived in New York, literally 100% of my local friends used wash-and-fold and owned nothing to take care of clothing. A close friend of mine confessed recently that he hasn't prepared a real meal in years; his kitchen cabinets are nearly empty.
The sharing economy is pushing this further. There's a tool-share co-op in my city for those things you need once-in-a-while, like a ladder. Car2Go and ZipCar mean people don't need 2 and 3 car garages at all anymore.
I can't wait to get rid of more stuff!