Edit: obligatory explanation (thanks mods for squaring me away)…
What you see via the UI isn’t “all that exists”. Unlike Reddit, where everything is a black box, there are a lot more eyeballs who can see “under the hood”. Any instance admin, proper or rogue, gets a ton of information that users won’t normally see. The attached example demonstrates that while users will only see upvote/downvote tallies, admins can see who actually performed those actions.
Edit: To clarify, not just YOUR instance admin gets this info. This is ANY instance admin across the Fediverse.
alternatively, if votes were private, you could spin up a bot network to mass upvote your comment; making it far more influential as most people are more inclined to believe statements they think others also feel. thankfully, votes are open, so you can’t
as long as there is a system, people will try to game the system; and when there is a new system, people will come up with new games