Why do people say to never run Minecraft as root?

I never understood this. It's much more convenient to be able to log in on your account, and be able to do anything right away.

Minecraft doesn't have any security exploits, and if I have a randomly generated 36 character password, with fail2ban, why must you tell me not to run as root?

 

[citation needed]

Running Minecraft as root is not necessary, Minecraft doesn't need root privileges, so why take the risk?

If there were an exploit you are in big trouble if that exploit enjoys root privileges. And it's not only Minecraft, but in most cases many plugins running as well. Bukkit team takes great care to make dl.bukkit.org a safe source of downloadable code, but outright denying the possibility that either Minecraft itself or a plugin is exploitable is playing Russian roulette.

If you run Minecraft with a user with limited privileges, only enough to run the Minecraft server, and things go badly wrong, it only affects the actual Minecraft server, they can't delete your website or stowed away backups or do anything much outside Minecraft because Linux will just go like "Nope, sorry, you don't have permissions over there".