I can't speak for others, but, while we don't pin versions in the Dockerfiles for our build container images, we do version the images themselves. Reproducibil

I can't speak for others, but, while we don't pin versions in the Dockerfiles for our build container images, we do version the images themselves. Reproducibility is a continuum, not a binary. We've chosen a point on that continuum that we believe gives us the best trade-off between reliability and maintenance effort. 100% from-the-ground-up reproducibility would be ideal, of course, but there's a cost-benefit tradeoff, and we're not being paid to be perfectionists.