I would say it definitely is worth learning, at least the basics with some advanced drawing skills.
Learning to draw faces and bodies will help you understand the human anatomy from an artistic side better and transfer into your 3D characters, since you are probably going to sculpt faces etc.
In my opinion I would even go as far as to say that they go hand in hand, since building a 3D character based off a concept art piece is a lot easier and smoother to handle than just starting to build or sculpt a rough idea that’s only in your head.
