There is a standardized API for package tools to expose and invoke editable-install functionality [1] which pip install follows, but Poetry didn't implement this API before (I see it does now though as of this past February [2]).
In other words, this a more thorough explanation of my point from [3]:
> Yes, if you ran poetry install you could get editable mode, but that requires every single end user of your package to install poetry and explicitly invoke a poetry install just for your package. And if someone else's package uses a different package builder, now they need to install and invoke that one. And on and on, and you end up with a six-hundred-line install script because of all the one-off "must install this developer's favorite package manager to use their package" stuff.
