Electoral votes are private in essentially all elections. The existence of an exception doesn't change the fact that most people have an expectation of privacy while voting. This clearly extends to internet forums or else we wouldn't be having this conversation.
The reality is the votes are already not private on the greater platform.
It is also possible to tally your total upvotes but the developers made a conscious decision for the site not to display this information. This is a lesson learned from reddit where you can observe toxic behavior from people trying to increase their karma score. It doesn't matter that you could technically do this on lemmy, you don't see the behavior because the design doesn't encourage it by default.
Why does reddit and until now lemmy not show voting history? It's a lesson learned from digg where showing vote history results in tit for tat voting blocks where essentially no posts could rise organically on their own merits. The fact that moderators can see vote history already allows action against vote harassment without the possibility for voting blocks to emerge. Again it doesn't matter if some nerd can technically find a way to view the votes, without it being part of the default design the voting blocks won't naturally emerge as they did on digg.