MacBook Pro Retina or MacBook Air not sleeping when closing the lid?

This only seems to happen to the MacBook Air and MacBook Pro Retina.  Why?
I think I finally have the answer: They do not have built-in network ports.
Most people use them connected to both power, and a wired network port, through an external adapter when working at the office.
When leaving for the day, you close the screen, unplug the power, the network, and leave.  Tomorrow your battery has died, and you cold boot. But only sometimes.  Why?
In System Preferences, Energy Saver, Power Adapter it has a setting to "Wake for Network access".

So, after closing the lid and going to sleep:
If you unplug the power cable first, then the network, your MacBook stays asleep.
If you unplug the network cable first, then the power cable, your MacBook wakes for the network event, and never receives a new sleep instruction, as the lid stays closed.
Case closed.