This question already has an answer here:
I still have a question. Since the "root" user has all privileges, why is
root ALL=(ALL) ALL in
/etc/sudoers on Linux systems?
## Allow root to run any commands anywhere root ALL=(ALL) ALL
I tried to comment it out, and the root user still had all privileges, it doesn't affect the root user at all. It looks like
root ALL=(ALL) ALL is useless.