npm is equivalent to combining pip and virtualenv into a single tool. This gives better ergonomics when switching between projects since you never have to "activate" your environment, it's always activated when standing in the project directory.

Isn't this what Pipenv does? What has been a downer for me is that many of the cloud providers do not support pipfiles in their serverless app services (Elastic Beanstalk, App Engine etc.)

On second thought, at least on GCP I should be able to put the pipfiles into .gcloudignore and just update the requirements.txt file with each new commit using git hooks, build scripts or a ci/cd tool.

Yep, correct. Unfortunately I had quite a few issues with pipenv - mainly around its relationship with pip.

That does sound convenient. I wonder if the virtualenv aspect is relevant though, i.e. do people really deploy npm apps outside of a container/isolation layer?

I imagine if you're deploying docker, you probably should be developing in docker (e.g. using PyCharm's remote interpreter/docker interpreter integration).