Experienced designers have often gone through hundreds of ideation rounds exploring form and design details.
If you have a good grasp of the product, you have a mental library with hundreds of potentialities and to draw these out would be pointless if you already can make an informed decision as to what the product is going to be. If there are limited resources, you may well step to creating the production file from step 1. However for more complex products we would always want to see some sketches and explorations - as long as you can reason towards the chosen design. If it is just for communication or artist impression purposes, we often start in CAD and add a sketchy feel if that is what the client desires.