Well, I will come to the very strong defense of the Tiny House Movement (not necessarily the TV show).
The folks who are building and living in these houses are very much aware that they could have bought an RV. They make the conscious decision that they want the natural building materials and aesthetics that most tiny houses offer. Most of these houses are much better insulated than an RV and totally capable of withstanding severe winter weather on a regular basis.
They also offer the owner/builder the opportunity to build their own home at a great savings, some for as little as $5000 - $10000 and a year or so of sweat equity. Going this route assures the owner that they can fix virtually anything that goes wrong down the road.
Most owners of these tiny homes do not consider them travel trailers, but movable homes. Most are well aware of the difficulties in actually moving them on a regular basis, and do not build them for this purpose. That said, a college student can build his own home mortgage free before or while in college, save TONS of money on rent while going to school, then when he or she get a job can move the home to their new location. When they get a new job in another state, their home can come with them. The aesthetics of these tiny houses can be as spartan or as elaborate as the builder desires.
Regarding holding tanks, you have options. Holding tanks are a pain in the butt (no pun intended) for year round, cold climate living. Most builders choose to go with either full plumbing directly to a sewer, or they design and build (or buy) a composting toilet. Showers can be as sophisticated or as bare bones as you desire, from fully plumbed with on demand heaters to as simple as a pressurized hand pump sprayer filled with warm water and taken into the shower stall with you. No reason you couldn't build a holding tank into a tiny house if you really wanted one, most folks in this movement do not want that option. Those that do, often use the "Honey Wagon" slid under the tiny house, out of the way and not taking up indoor space.
Most appliances come from either the RV industry, or more often the boating industry - alcohol stoves for cooking,
propane fireplaces which hang of the wall for heat, some choose to go with tiny little wood stoves for heating. Most use either on demand
propane water heaters, or small apartment sized tank models. Refrigerators are generally just small compressor models, MUCH cheaper than the dual fuel RV unit, and since the house is seldom moved, this makes perfect sense.
MANY of the tiny house folks would be perfectly happy and prefer to build their tiny house on a permanent foundation, but most of our governmental units in North America will not allow it. The purpose of building codes was supposed to be safety concerns, yet the building industry has deemed homes smaller than 900 or 1000 sq ft to be inappropriate for some reason (money, bigger homes means more money in their, and the bank's pockets). People who want to live in a small, aesthetically pleasing house built of natural materials have found that building on a trailer is the easiest way to get around our "big brother" government, since trailer built homes are not subject to the same building codes. Most folks who design and build these homes follow all reasonable codes for
electrical, plumbing, construction, etc. They just ignore the totally arbitrary size requirements.
In case you haven't realized, I came to consider an RV after years of researching and planning to build a tiny house. I have just decided that I would like to do some full-time traveling first, so an RV makes more sense for that. But for permanent living, in limited locations, I still do not think an RV would hold a candle to a tiny house.
By the way, I do not believe they are a fad. Though not everyone's cup of tea, they have a definite place, and should be an option, for those who choose to live small, with low maintenance costs, low utility cost in a mortgage free home. As stated, some communities are finally starting to implement some reasonable reforms to building and zoning codes, but not near enough.
It seems to me this type of community(this forum), so accepting of the full-time RV lifestyle, and all the reported rewards of more time, less cost and less time spent maintaining your "home", should be a natural ally of the tiny house movement. Most of the responses so far have been very disappointing. Why shouldn't a more stationary person be allowed to have the same benefits so many tout in RV living? I really do not understand the extreme negative attitude.