The tradition has been around for a couple thousand years.
Why did it start in the first place ?
The answer to that may have a lot of bearing on the question.
FTA;
"Historical references to a condemned person’s last meal go as far back as ancient Greece, China and Rome, Hayes said. Some of it is apparently rooted in superstition about meals warding off possible haunting by condemned people once they are put to death."
I doubt that all those cultures did it for the same reason, their beliefs varied to greatly.