I'm struggling to think what security risks there could be to knowing who is allowed to use
Being able to target a user with sudo priveleges makes compromise easier. Same reason /etc/shadow is ro root. Security through obscurity thwarts more attacks than its' given credit for.
- needless leak of information; if any account or process is compromised the attacker may then read the sudoers configuration and use that information to figure out next targets (accounts, allowed programs, ...)
- needlessly world-readable files may create conditions for denial of service attacks e.g. Sendmail files and locking mechanisms https://securitytracker.com/id/1004368 (world-readable files can also be opened by many processes; this may slow down I/O performance on the file which is probably not relevant for
sudothough may be bad for a database or logging daemon)
- unknown vulnerabilities that let the attacker do something really clever via some almost forgotten
ioctlor buggy audio interface that the needlessly world-readable file gives them enough of a toe-hold to climb