Not all new features are created equal, and this particular change has us kind of scratching our heads wondering why Google would consider it a good idea. In Lollipop, you can now access your quick settings straight from the lockscreen. This way you can toggle Wi-Fi, cellular data, and Bluetooth without unlocking the device, even if it's secured behind a passphrase.
In the case of theft, this gives a burglar the ability to disable the data connections necessary to track the phone. Granted, this concern isn't new. KitKat already allowed people to toggle Airplane mode without unlocking the device, effectively doing the same thing. This just gives folks more granular control.
With more options available from the lockscreen, it makes sense why Google decided to remove everything from the power button except for the option to turn off your device. With airplane mode accessible from Quick Settings, and sound reached through the volume keys, there's little need for duplication from an interface design point of view.
But in terms of security, we're left a little uncomfortable by the decision. There's already a ticket open to get this addressed. It just remains to be seen if Google actually will decide to pull back on this change.
Thanks, Oscar Cerna.