Maybe not 2D as "art", but 2D representations of 3D objects might be useful. Be it on screen or paper, objects are still displayed in 2D. Only by adding light/shadows we see them as 3D objects. i hope it makes sense.
It is often beneficial for 3D modellers to be capable of drawing a model sheet. In a large company they may employ concept artists specifically for the job. You don't need to be a Michael Angelo but rough sketches of your model are helpful for 3D artists.
There are many aspects of 3D asset generation from concept art, modelling, uv unwrapping, texturing, lighting, rigging and animation. Not every modeller is going to be an expert in every field but they need to know at least the basics of each aspect of the pipeline.