About ablation study and L_Q loss

[imabackstabber]

Hi,I'm wondering why ablation study in paper doesn't give result of using L_Q loss only.If the result is obviously worse than using L_C only,it will demonstrate what a role that L_C is playing in this task.
Also,I'm also curious about why using a loss that forcely pull prediction points to predefined hash center,which is a singular point that is hard to converge to(and I know that part is talked in paper).I just want to know why create a such a loss function and how much the importance is.
Your reply will be highly appreciated.