Buildpacks IMHO suck for reproducible builds, unless you in all versions, and even then it can be hard to find out what you are really shipping. For serious (large, whatever that means) projects this is a huge problem. Docker/Containers solve this problem nicely. Developers do not have to know all the details about base images. Just build a decent base image for them once, say for JVM if that is would they need. As others have pointed out, there I no need to use Dockers build files approach, there are plenty of better alternatives out there.