If you have policies enforced to prevent mcafee to be disabled then this wouldnt happen. If the machines have the agent installed but not mcafee, you can created a report to check for machines that do not have it installed however, if a you a proper deploy ment task it would rectify this automatically. Which version of ePO are you using?
It's a valid question. There are times you want to know if McAfee isn't running. We had a number of Windows 2000 Terminal Servers that were downgraded from VSE8.7 to 8.5. None of them had McAfee running because they weren't rebooted after removing 8.7.