Pure luck, only upgrade I ever got as a *S was NRT-LAX I lost my boarding card and had to ask for a new one and they had like 10-15 upgrades they were doing so I just got the upgrade instead of someone else that were to slow to get to the desk.

Only *S worth is with SK (my silver program) I get a extra bag flying SK and in the US I get to use the premier lines flying UA, checkin and security where available thats about it but better than nothing .