Why do people struggle to sympathize with adults?

So, from time to time, I watch true crime videos, but in the comments, people are always like, 'Poor dogs' or 'Poor children.' Yet no one seems to care about the adults who died in the video. In fact, people even request to see photos of their bodies. I’ve seen many arguments about why trigger warnings are needed for dogs dying but not for adult humans. The reasoning is often that dogs and children are 'innocent' and can't do anything wrong.

But that’s such a naive outlook. Children are capable of hurting others—sure, you can argue it's because of an abusive home. But there are children who come from non-abusive homes and still hurt others. And what about the adults? What have they done to not deserve your sympathy? Lying? I don’t get it. There are adults who’ve never hurt a soul in their lives, so why can’t they be considered 'innocent'?

I personally struggle with hearing about children dying and need a trigger warning for that, but I still feel heartbroken for the adults who died too. Maybe not the same way as for children, but I still care. I think this bias has a lot to do with people having pets. They empathize more with dogs because they imagine losing their own pets, or they witnessed their pets dying so they understand the pain, it does have nothing to do with 'innocent'. But that doesn’t mean we should overlook the humanity of adults who’ve suffered or died