I guess it is simply rare these days because there are just too much of us SENs flying around - and it's additional efford for the cabin crew to remeber the names and takes it's time. In my FTLer days I was never greeted on LH flights, being Silver on BA it happened more often on flights to LHR.
Think it's more down to the route and staff and how filled up the flight it - but that's just guesswork.
Was a surprise to me that even in F (SIN-FRA) they sometimes skip this... they should take their time for those passengers IMHO!
Cheers
muc_flyer