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.
It might also increase quality though. If people downvote out of spite and now it can be proven that they did, they might not do it and thus remove “bad” downvotes from the pool.
I still think in total it’s probably better that they can not be seen, since anonymity usually gives more honest opinions.