On newer versions of Windows even being logged in as a local Administrator does not raise the account to the highest administrator privileges. So running Vantage with the "Run as Administrator" allows Vantage to access system information such as the registry or system events that it would otherwise not have access to.
Think of it as if there are three different account types on the computer; a common user account, an administrator account, and a super administrator. This latter is usually hidden and is more powerful - basically it can do anything on the PC. The lesser administrator accounts can't do everything and are pretty close to being a common user account, but they are allowed to elevate their privilege level to full Administrator. When you "run as administrator" you are, for that command, using this more powerful super administrator account.
So basically even tho you're logged in as an Admin unless you constantly tell it "Run as Administrator" you are actually running more like a common user or lesser admin.
Microsoft invented "UAC" (User Account Control). What UAC does is REMOVE your administrative privileges when you log on to an account that has them. If you run a program that requires administrative privileges, UAC warns you that a program is trying to acquire them and lets you permit or deny. This was done to attempt to protect users from installing or not knowingly installing programs that may be bad. eg. Going to a website that installs malware.
I hope that helps explain the reasoning behind having to "Run as Administrator".