Anyone who does Web-scale or information technology over the past two years knows containers. The primary reason is the success of docker in making not-so-new containers easy to build, deploy, manage and use.
Personally, I think Docker containers are great. They provide a far more efficient level of isolation than VM virtualization, without sacrificing manageability.
Docker itself, however, is a young company, and every now and then young companies, whose products are moving very quickly, make silly mistakes.