haha... for me it is just a technical matter.  Example: if you lost your S8 when you are out for lunch somewhere.  Someone else might have stolen or pick up the phone left unattended.  Most likely we are just worry whether our precious data inside will be used by others.  In such typical situation, most likely the fellow will not have a photo of you to unlock your phone even if the phone can be unlocked with a photo.

anyway, we shall try it out after we get our S8. 

btw, can the latest Samsung phones like S7E and Note 7 be hard-locked by owners?  Meaning if one do not have the password or authentic way to unlock the phone, it will be locked forever even if you hard reset the device.  I think latest Iphone has this anti-theft feature - correct me if I am wrong.