Python does not really have a "build" step. _That_ is the problem. I think Heroku also played a role in prolifirating the idea that you can just push your code

Python does not really have a "build" step. _That_ is the problem. I think Heroku also played a role in prolifirating the idea that you can just push your code (from a git repo) to a server, and the server will take care of deploying it. Which usually means the server will install all the dependencies from pip during the process.