I don't think it's the act of vaping that's corny, I think it's the fact if someone vapes - they're constantly vaping. Same way with weed. It's one thing to vape occasionally throughout the day but you will ALWAYS see it in their hands. They can never set it down or let it go. They bring it into establishments and places where smoking in general is not allowed. I think the corny aspect is the clear inability to self regulate, and if you ever mention it to someone who vapes/smokes weed they go feral. It's not normal in any other context, this behavior is deemed weird in most contexts.
With that being said, I agree people shouldn't really comment on it or care. I only really find it mildly corny and I don't sincerely think of anything when I see someone vaping/smoking in general or in public or whatever. It's their choice at the end of the day and it's weird to care that much about it.