When people move to a new place, they typically bring their car, clothes, personal belongings, family, and pets with them. But in almost all cases, they leave their home.
Why don't we all have nice homes that can be packaged up onto a 40 foot trailer in a couple of days and shipped to our new destination?
Surely there is sentimental value in keeping one's home (even if it's in a new location), and an expandable or modular frame would make it easier to grow or shrink one's home instead of constantly replacing it as one goes through the various phases of life.