As both an SCCM and a passenger I can't bear it - sounds so false & at times patronising.
When operating as an SCCM I prefer to thank my collegues individually at the end of the day - it far more appreciated than a cheesy PA.....it also lets me recognise each crew members respective efforts at an appropriate level.
Within BA it has never been official policy to do this (for the 16 years I have been there anyway), & when it happens it is entirely on the initiative of the Flight Crew or the SCCM concerned.