Originally Posted by
chris63
Press the call button, that is the reason for its existence

Indeed. The alternative is a standing buttler. But then passengers would complain about the lack of privacy.
I am a very infrequent F flyer, but I tend to go the the galley myself if I need anything, rather than even using the bell. Also, I am not sure than many passengers seek immeidate contact with FAs when they wake up in pyjamas.