I saw a segment on Book TV with some economist (unfortunately, I don't remember his name).
He said that the average American house purchased in 1980 was 1,600 square feet. The average American house purchased in 2007 was 2,300 square feet. What accounts for this nearly 50 percent increase in size?
The economist said the primary reason was the access to good public schools. You have to buy at least the average-costing house in a good-average neighborhood in order to get your kids into a good public school. So there is a competition to buy bigger and "better" houses, whether they are more strictly speaking needed or not just to provide shelter.
The Ikea house is about 750 square feet, so just about half the size of the average 1980 house.
I would imagine that the market for such housing is skewed toward empty nesters, childless couples, single persons and the like.