Anyone else's players always wanting to butcher the monsters they kill? Harvesting hearts etc.

It seems so often my players kill a weird creature or mini boss then I'm met with a question like "Can I cut it's heart out? Can I slice it's scalp off? Can I rip it's teeth out?".

But I've even noticed it from watching other actual play DnD shows. It's happened in Critical Role a few times.

Why does it seem like there are so many players like this? I've got people walking around with a big sack of rotting hearts with seemingly no intention of doing anything with them.

I'm going to have to start acknowledging it in game so they realise how ridiculous it is. "I try to flirt with the guard so they let us in", "ok, the guard holds back a vom at the stench coming from your bag and tells you to get lost".