Some Jewish adults choose to read it precisely to understand what was going on in the mind of the tyrant who terrorized and murdered their kin. Matt Lieb mentioned in an episode of Bad Hasbara that his father owns a copy. I know an Ashkenazi physician who read a copy. I have a (mostly unread) copy on my hard drive. Mein Kampf is simply the most obvious place to start researching German Fascism (though by no means the best).