It's a fact that 3D televisions are more expensive. But even if most TVs these days come with 3D capabilities whether you want them or not, it's not like the TV itself is the only expense. To take advantage of those capabilities you've also got to purchase expensive 3D glasses that often hover around the $100 mark.
Multiply that by the number of people in your family and it's not difficult to see why most people have chosen not to bother with living room 3D. The real question is how Sony and other companies could have possibly thought that many consumers would go in for all that extra expense on top of a pricy TV in the first place.