Why should I create a new user for VPS?
Your superadmin user's name in Linux/Unix systems is "root" by default. Therefore, hacker may attempt gaining access to your server by compromising the password. To avoid this you should always create a new superadmin user for your new VPS/dedicated server.
In FreeBSD, for instance, ssh access to "root" user is prohibited, while Debian and Ubuntu require you to create a new user during OS installation. Having superadmin user with non-standard name makes your server much more secure.
Please keep in mind though that main role in keeping your server secure lies on using the latest versions of software and using strong passwords.