Keep in mind, when this solution was adopted Docker were still wedded to Swarm. Even if they stop caring about it -- as they pretty much have now -- we have a system that works at rest. Two years on, the team(s) that handle the production support and operations are more comfortable with Docker & co, because of this. Not to forget, this is a very large (and risk-averse) enterprise. You don't always get to pick whatever you like!