Simply put, Shipping containers do not provide dimensions that are comfortable to live in with narrow widths and low heights.
The rectangular box hardly makes an architectual statement - but more importantly there is limited customization in containers. There is no option of raising ceilings and window glazing and skylights are difficult to build into these sheet-metal boxes.
Shipping containers are afterall designed to be secure and unbreachable to safely move goods.
Any modifications to the structure require welding and expensive reinforcing steel. Structural integrity is greatly reduced with modifications of the unit.
When moving, installing and setting up containers, a team of workers is required with the addition of a mobile crane.
This is both costly and limits the areas n which containers may be moved and constructed in.
Set up areas must be large enough to accomodate a mobile crane for delivery and container assembly requires significant time to bolt steel shores and framing.
Normally straightforward tasks like electrical, plumbing, painting, and trim work can take several times longer when working with containers due to limited access pathways.
Shipping containers do not conserve heat or airflow and instead trap the cold in their cornering. Their basic design is not energy efficient and they do not promote air circulation resulting in cold spaces and increased heating bills.
Their steel framework is prone to rusting which again can affect structural integrity.
Flat container roofs do not promote run off of rain or snow. Similarly air flow collides and pounds with the structure and is not channeled away.