You're describing it backwards. The inability to have empathy is a symptom of anendophasia, the lack of internal monologue. The part where you may care is it used to be extremely rare. The original studies had to be done in prisons. It's not rare anymore, and they've softened the definitions.

The absence of an inner monologue, a phenomenon known as anendophasia, is a genuine neurological variation where individuals do not experience verbal thoughts or a "voice in their head". It was once assumed that inner speech was a universal human experience, but recent research indicates that this is not the case. People with anendophasia think in other ways, often relying on visual imagery, abstract concepts, or feelings instead of words.

The definition used to place these people in the same lines as sociopaths. But, the definition of that family of diagnosis is too mean now that it is no longer rare.