Exactly, for a busy celebrity, having a canned answer is a polite way to acknowledge a fan and give them a little thrill. They don't have time for a genuine, heartfelt conversation with everyone they meet.

While this is true, it also means they're not someone I want to converse with so it makes it easy to move on to someone more interesting.

I was more thinking about celebrities, influencers or con exhibitors, where a fan-celebrity relationship may exist, but not a real relationship.

Same goes for politicians, though there it becomes much more problematic.

If you got this with people that are actually close, there would be a problem.

Indeed. Canned responses are a defense mechanism for being in awkward social situations. Making it more awkward is maybe not a great move.