system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How does Vader get so many dirty finger prints on his helmet, when it's the machine or his gloved hands that removes it?

You will see time and again, in some scenes in Rogue One and in Return of the Jedi when he saves Luke.  Is there an "in-universe" explanation for this?
gpt
It's well known amongst the 501st that touching Vader's helmet brings good luck - or gets you a cauterised stump, force-choked and thrown though the nearest bulkhead into the hard vacuum of space. One or the other.