This feels like moving the goalposts. This is on a thread which began with the statement that Docker is reproducible. Will we next be saying that, OK, it's an i

This feels like moving the goalposts. This is on a thread which began with the statement that Docker is reproducible. Will we next be saying that, OK, it's an issue that Docker isn't reproducible, but it's doing it for a noble reason? Regardless.... I can give a few reasons that it matters, off the top of my head: 1) Debugging: It can make debugging more difficult because you can't trace your dependencies back to the source files they came from. To make it concrete, imagine debugging a stack trace but once you trace it into the code for your dependency, the line numbers don't seem to make any sense. 2) Compliance: It's extremely difficult to audit what version of what dependency was running in what environment at what time 3) Update Reliability: If you are depending on mutable Docker tags or floating dependency installation within your Dockerfile, you may be surprised to discover that it's extremely inconsistent when dependency updates actually get picked up, as it is on the whim of Docker caching. Using a system that always does proper pinning makes it more deterministic as to when updates will roll out. 4) Large Version Drift: If you only work on a given project infrequently, you may be surprised to find that the difference between the cached versions of your mutably-referenced dependencies and the actual latest has gotten MUCH bigger than you expected. And there may be no way to make any fixes (even critical bugfixes) while staying on known-working dependencies.