As far as I can tell, there are two types of companies in the Docker ecosystem (and, by extension, in the ecosystems of all rapidly growing projects). The first type of company was born with the vision of delivering something it believes is missing in the project. In the case of Docker, perhaps the epitome of this is Weave, a UK-based startup that identified some glaring holes around networking with Docker and set out to put that right.
On the other side are the companies that see an initiative with traction, and declare their solution, all of a sudden, applicable to that project. These types of companies are either large (read slow, monolithic, and generally blind to innovation) vendors who simply want to be able to “tick a box” for their customers. The other, more unfortunate souls, are those small vendors who, through no fault of their own, were caught out by the ascendency of a project. Their happy little world all of a sudden doesn’t exist or is irrevocably changed, and they have no option but to jump on any life raft offered by the upcoming initiative.