Shipping containers bring modularity that is unparallelled which has boosted trade largely. A quality that the construction industry has severely ignored in the past. No matter how much we demand customization, urban living pushes for modular construction in a lot of ways at least in spatial planning (eg. Apartments, Condos). The quality of modularity is unavoidable when the rise in housing demand is so high and time is crucial. 

Rising rents in urban areas and shrinking the quality of living is a huge problem urban areas face. The biggest components of this cost are - 1. Land Prices (Which are impossible to change) or 2. Construction cost (Which can be brought down through various strategies)
And modular construction may be the only known way that can do it.

The prices can not only be offset by faster construction but quicker making times as well. This is the biggest reason, despite the availability of containers on a port city, it can be a point to explore manufactured housing as a concept especially for dense urban areas.