Handling a smart phone is already stressful enough. You can't touch the entire front of phone in fear of accidentally tapping something, even if the screen is off because it might turn on at any moment. With tap to wake you have to worry about just bumping it and with facial expressions you'd literally need to be concerned about just looking at it funny.
Somehow, I think Apple probably thought about this before making a change to their flagship phone. They have many options, including making the "tap" a force touch. So requiring a certain amount of pressure before actually turning on. Or requiring a double tap. Or being more of a "tap to unlock" using raise to wake.
They stopped thinking when Jobs died. Now they're just taking his last known visions to foolish extremes. Sadly, the rest of the brands just blindly follow them, so it won't matter, they'll still be "ahead" of everyone else.