Yes, the hook grip can be uncomfortable at first. So why do we emphasize the hook grip so much? Why not let people just use whatever grip they are most comfortable with?
CrossFit is about efficiency, not comfort.
Simply put, the hook grip creates friction that prevents the bar from slipping out of your hands. When the barbell slips (regardless of how small that slip might be) you lose power. Another benefit of the hook grip is that it aids in grip fatigue. Your fingers create a “clamp” that actually benefits your grip, allowing your hands and forearms to relax during lifts, rather than using full force to grip the bar tighter.
In the Olympics, weightlifters compete from all over the world. They each have their own technique and very particular ways of approaching the lift. The ONLY thing that stays the same for all contestants is the use of the hook grip. A worldwide agreement means there must some advantage to it! That makes a rather bold statement in regard to the validity of the hook grip.
The hook grip is a bit awkward and you may experience some discomfort, but give yourself a few weeks and it will get much better. Soon enough you won’t understand how you ever lived without it!