The voice command 'OK Google' is mostly used from the Android desktop to later launch a voice command that manages to perform that great variety of actions from the comfort of dictating a reminder with our own voice. The recognition of voice commands has improved considerably, so the use of 'OK Google' is increasingly useful.
If we look at the different high-end phones or more substantial phones that we have had lately, such as the S7 edge, Priv or P9, they all lack from the "always on" functionality of 'OK Google' to wake up the phone from the screen off to have it ready to perform any of those actions we are used to. The V20, LG's new phone, is the exception.
The reasons given by manufacturers range from problems to device security, conflicts with other types of similar services such as S Voice and due to the limitation that may mean that the chip is limited to offer Ok Google's 'Always on' feature. Also the battery consumption that it can produce, it even manages to be the users themselves who deactivate this functionality.
It is the LG V20 that offers appropriate support for this feature that, with the arrival of Google Assistant and Google Home for the next few months, it will have its importance for an Android in which voice commands will take on their importance. The ability to activate the smartphone with voice commands from when the screen is off is going to be a feature well desired by many. This makes our smartphone a device closer to the future and those science fiction movies than that phone from last year much more limited in functions.
It's a shame that users don't know how to use Ok Google
The LG G5 also has this feature.