As I understand it, gesture drawings are for distilling the movement or flow of a pose into its most basic expression, similar to how we do the same for forms and shapes. Then once we have distilled that essence, we build on top again. The exercises help to train your hand and eye to focus only on the most important aspects, and avoid distracting details at this stage. They are great for practicing and experimenting with poses and flow without getting too bogged down in details. That said I too am a beginner, so my understanding may be flawed or incomplete.