He answers without much hesitation: "The same reason I should for you, I guess."

It sounds harsh when it's presented that way. Unlike her, he doesn't want to hurt her. That... was definitely too much effort and ill-will for him to muster, both in the act and the aftermath. And in any case, he was invested in her in some way, whether it was as a support or as a friend.

That, he can't deny.