Boeing 777 Autothrottle
After reading the Asiana 214 thread and doing some further research, I get the impression that most airlines that operate the B777 mandate the use of autothrottle in all phases of flight, even when handflying, and Boeing recommends so.
Now I'm wondering, why does the B777 need to be flown with autothrottle?
I understand that on the FBW Airbus use of autothrust makes sense because the artificial flightpath stability can lead to speed deviation (yet many airlines allow manual thrust in manual flight on the Airbus).
I understand that on conventional aircraft, use of autothrottle while handflying is not recommended because of thrust-pitch coupling, which does not happen on the B777 due to FBW control laws. So is autothrottle recommended for handflying on the B777 simply because there is no reason against it (as on other types), or is there a specific reason for it (on the B777)?
And another question: If autothrottle is used for a manual approach and landing, is it used until touchdown? If so, does the autothrottle automatically retard the thrust levers or is that done by the pilot?