I know that it's just a few simple operations for me to do it myself, but npm has spoiled me.
This is a missing feature, there are various hacks but nothing concrete.
If you're working on a large project you have to keep track of all your dependencies and preferably only add the main dependency, not its dependencies, into requirements.
I tend to avoid doing pip freeze > requirements.txt because it lists packages I know shouldn't be in requirements.
Like civilian, my main ask for an improved pip would be a way to save a single explicit package into my requirements.txt by adding a --save flag when installing it.
I don't want to include sub-dependencies in my requirements.txt.
The way to maintain requirements.txt with single dependencies (base dependencies maybe, I'm self-taught on the lingo), is to manually add them one by one.
Pip freeze is useless because it adds a lot of things you don't need into requirements, making it cluttered and hard to follow.