It's a bit idealistic to think people can "just" use fat binaries; sure, Go mostly handles that (not completely; by default most nontrivial Go apps are dynamic,

It's a bit idealistic to think people can "just" use fat binaries; sure, Go mostly handles that (not completely; by default most nontrivial Go apps are dynamic, which you can fix but not that easily) but that's not exactly any comfort if I've got 30,000 lines of Python which I'm not keen on rewriting. Technologies like pex can help but in practice require some work, especially with a codebase that hasn't been written with it in mind or when dealing with third-party libraries that aren't expecting such an environment - and that still doesn't solve what you're doing with the interpreter itself. I'm far from a big fan of Docker, but can definitely see the appeal for providing a solution to those problems, even if some see it as unprincipled. In our case we'd already put a lot of effort into building mostly self-contained binaries and Docker is still useful (admittedly mostly just as a component of Kubernetes; we'd cheerfully replace it with rkt or something if there was a good option).