This question really stems from the fact that I'm perhaps unfamiliar with the true function of FileVault. As far as I can tell, there's a way to force a pre-boot login screen... which means that, by default, FileVault logs in automatically at boot? Otherwise, the OS wouldn't be able to start.
So if FileVault automatically logs in to start the OS, does the encryption serve any function at all? I created a standard User to test this and was able to view all my files without entering any Administrator password – the only files I couldn't see were due to not having permission to view files from other users (which is standard protocol regardless of encryption, if I'm not mistaken).
Can anyone explain the function of FileVault to me? I'm starting to wonder if I'm using it to serve a purpose it wasn't intended to serve.
(For reference, I'm running macOS High Sierra)