From a Wall Street Journal online article:
The jewel-box home—small, but loaded with amenities and costly finishes—is luring more home buyers. An analysis by Home Innovation Research Labs, a subsidiary of the National Association of Home Builders, found that the number of new-construction luxury homes at 3,000 square feet or less has increased nearly 20% since 2013—with a corresponding decline in larger-size, high-price homes.
Changing demographics might be driving the trend. More than half of all households now consist of single people or couples, U.S. Census Bureau data shows—with traditional nuclear families accounting for just 20%.
“Empty-nesters want to downsize, but they want luxury homes not starter homes—luxury kitchens, marble surfaces, all the latest and greatest,” said Tim Costello, CEO of Builder Homesite, a consortium whose New Home Source website—an online clearing house for new-construction homes—tracks home buyers’ preferences.
To read more: https://www.wsj.com/articles/luxury-homeowners-put-a-ring-on-jewel-box-homes-11576081060
The reality, however, is that modular, prefabricated housing can exceed the limitations put upon it by popular conceptions of trailer parks and postwar government housing. Not only are they certainly faster – an important factor in cost, as the cost of land and construction have as much as 
Economists say aging baby boomers are the biggest culprits because many are staying healthier later in life and choosing not to downsize. Some look around at the lack of smaller, less expensive homes and are loath to get into bidding wars with their children’s generation to get one.
Boomers Daily 