I've long switched to Emacs/Org, but used JupyterLab extensively before (as a data scientist).
It's way more powerful than vanilla notebooks since you can open notebooks/code/related side-by-side, easier to extend (with lab extensions), etc.
I always thought people only still used vanilla notebooks because that's what people say they use, e.g. "I work with Jupyter notebooks" (even though that may well be in JupyterLab). So most regular users wouldn't necessarily know about JupyterLab.
I have used org-mode/babel as a notebook replacement, and obviously the flexibility and the editing capabilities are vastly superior to Jupyter notebook, but I fund it sluggish. I assume that, at least in my setup (using babel-python), the kernel is invoked synchronously. I also didn't try to get any form of completion working, but it should be possible and it would be nice to have.
I always thought people only still used vanilla notebooks because that's what people say they use, e.g. "I work with Jupyter notebooks" (even though that may well be in JupyterLab). So most regular users wouldn't necessarily know about JupyterLab.