Why not the real Sam ?

Could be any number of reasons - and one of them could have been that he just flat out didn't want to do it.

What I thought was weird is with the "new" Sam, he comes in dressed as Santa Claus. He doesn't disguise his voice or anything, yet no one - particularly Alice - has any idea who he is until he pulls down his beard.

In the early 1980s Allan Melvin appeared as a regular in "Archie Bunker's Place", a successor to "All in the Family", in which he played the role of Barney Hefner. When this series ended in 1983, Melvin's work was exclusively devoted to cartoon voice-overs. Melvin died of cancer on January 17, 2008 at age 84.

In "A Very Brady Christmas" Sam The Butcher was played by Lewis Arquette. Arquette died in 2001 due to congestive heart failure.

He is still beating his meat last i heard.