http://i.imgur.com/allxzAQ.png
The reason this stuff is buried in a 2nd-level menu is that you're not supposed to need it. It's power-user stuff. Normal users are expected to either close the lid or press the power button, as they do on every other type of computer-y device now (phones, tablets, ereaders, etc). Software power buttons were a UX mistake this OS is correcting.
On your edit, I believe 'power-user' is a strong term. It was only a decade ago when pressing my power button could mean corrupting documents. These ideas stick.
Locking the computer when I walk away at work is common work. Leaving an unlocked computer at a financial institution is a dangerous scenario. These are Excel wizards, data entry, and so on who might be baffled by the premise of anything that is not Excel or Word.
Hitting the power button is not as intuitive as closing a laptop lid. The power button is considered dangerous except for turning on the computer by most normal users.
My wife knows (from some prior experience) that unplugging the computer without shutting down can be dangerous. She also knows that putting the computer to sleep will lock the computer and not let friends/child on the desktop without asking for a password.
I guess if I had a desktop PC at home, life would be different, but I haven't had one of those since 2001.
Or you can add a button to the start screen - http://www.howtogeek.com/77061/how-to-add-shutdown-restart-s...
The instructions are:
1) (Sometimes) when you hover in a corner a menu will popup or press WIN + C.
2) Click settings (in the midst of 4(?) other options)
3) Click the power button.
4) Click the desired state.
Way too many paths in that state diagram for a typical user. For the common tasks, I expect to make two-three transitions with limited, unambiguous, options. Some of my workflow has transitioned to passing four to five states (usually in Metro at this point), back to desktop, to Chrome to locate help, back to the beginning of the state diagram to perform my original task.