What? Ever used an Android device? Tap to wake is super useful and makes perfect sense if no physical home button.
1. Double-tap on the screen. Lockscreen appears.
2. Check the clock.
3. Fumble annoyedly until finding the power button to turn the screen off.
I guess they're worried about false positives. But LG solved this by only allowing double tap to turn off from any of the default apps (home screen, notifications, settings, etc). You had to quit out of third party apps to turn it off that way.