Actually people want both. Sorry either trend bothers you, but they are both quite popular.
Many folks are spending much more than they thought on what are basically RV's or trailer trash homes on wheels. Then, when they get them built for 3 times the price they thought it would cost, find out that local zoning laws prohibit them from rolling in the "tiny house" even if they own the property.
If you think I am all wet - Google it.