Newcomb himself was not a philosopher.

I think Newcomb introduced it as a simplification of the prisoner's dilemma. The game theory party line is that you should 2-box and defect. But the same logic says that you should defect in iterated PD, if the number of rounds is known. This third problem is popular in academia, outside of philosophy. It is not so popular in game theory, but the game theorists admit that it is problematic.