@B P (Ult1m4) because there's no reason to really care that deep. The reason it's a waste for him if she die is he can't fight her anymore. That's it (for now at the very least). He knew that there's his comrades to spar with so getting stronger is inevitable even without her. It's just that fighting her is a new experience for him. New moves offensively and defensively. Tho I'm not saying him wanting to save her is out of the question. Personally, i think he wanted to take her in but at the same time it's fine if he can't. He's a captain after all and she's a criminal.
I don't care about your taste!