[choeger]

That's a really interesting read. I bet the DIND pattern is very common because it is a) common to run CI jobs in containers, b) common (and a good idea) to describe testing environments in containers inside the source code repo and c) a good idea to use the same source for a) and b).

One particular instance is gitlab where the declarative pipeline demands a docker image. If your repository comes with a docker description for test execution, you are pretty much forced to run DIND.