Mac won't shut down

If I select Shut Down from the Apple menu and click on the Shut Down button, I expect the Mac to shut down. What I don't expect is to come back from being away for a week to discover that some random app interrupted the shut down and the computer has, in fact, been on the entire time.

If I say shut down, shut down. Don't second guess me. Don't put up random prompts. Kill what you need to kill and shut down.