system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Pettigrew’s metal hand was able to kill almost instantly because he hesitated to obey Voldemort. Why wasn’t every Death Eater required to have one?

If I were Voldemort, the Death Eater initiation ceremony would involve the pledges getting their hands cut off and replaced with the superior autonomous metal version.
gpt
Pretty easy way to spot the secret cabal when everyone has matching amputation scars one day.  It's better to show you trust some of your people to follow orders than make them feel like they're forced to do so.  Having pettigrew around was motivation enough that he could do it but chose not to because he trusted you.