Oleophobic coating
So I have an iPad 2017 which was bought in August 2018, from a week or so I bought it it was always having a tempered glass (9H with oleophobic coating) on it , and recently I started noticing more and more smudges on the tempered glass (more so with the dark mode, iOS 13 public beta) so today i took the screen protector off and the oleophobic coating of the screen itself seems to have worn off, how is this possible?