I've very rarely seen setup scripts that don't have implicit dependencies on the details of the host environment. Whether it's assumptions about the OS or file

I've very rarely seen setup scripts that don't have implicit dependencies on the details of the host environment. Whether it's assumptions about the OS or file system or what related software may be installed or whatever. Often because the original developer can't predict every permutation of the possible interactions because of a combinatorial explosion of possible system setups, sometimes because the script is poorly written, and very often because the language or tooling itself is poorly isolated (eg, pip and npm). Docker is a lightweight way of guaranteeing deterministic setup script execution. Obviously you can still screw it up by pulling from unversioned base images etc, but the numbers of failure modes are limited, typically easy to locate (ie within a single dockerfile rather than across an entire OS), and relatively easy to prevent with some best practices. And best of all, that's true across languages. I can achieve the same effects with pipenv, yarn, or other tooling specific techniques like folder level postgres installs. But then as a developer I have to know the thousands of idiosyncratic pitfalls that occur across the plethora of tools I have to deal with every day. And realistically, I have to deal with a ton of poorly written applications and scripts that I want to execute with some degree of isolation without a ton of overhead. More than I could possibly ever fix.