One factor to be considered is that the number of possible moves in a
backgammon games is infinite. The players could easily just keeping
hitting each other to infinity.

The number of possible chess games, while very large, is not infinite.
After a few billion moves the 50-move rule becomes a factor.

Except for the fact that checkers does not have a 50-move rule, the
number of possible checker games is relatively small.

None of this addresses the basic question being asked here, of course.

Sam Sloan