![enter image description here][1]
There's a few reasons for that - to prevent revenge/antirevenge voting for examples. To a limited extent mods will be informed of unusual voting patterns (though in most cases this is automated), but there's no way at all for a user to know, without a comment made by the voter of who voted on a specific question question. [1]: https://i.sstatic.net/5VYS7.jpg