AFAIK in the python 2 era it was the de-facto standard (just swap "python -m venv" with "virtualenv"). All these new tools have just made it more complicated and it's not clear to me what they gain, seems to me like they've simply succeeded in convincing people it's complicated by obscuring what's actually going on.
Correct. And most people back then were just using `pip install -r requirements.txt`, including different files for dev/test/prod as needed.
I worked at one company that used buildout back then, which seemed relatively rare, but buildout was more flexible and allowed you to do things like installing system packages or running your own scripts. We used it to pull down config files that weren't checked into the repo but still wanted to be shared, helping setup the local developer environment, and a few other things.
