Commentators making things unnecessarily difficult

Sometimes I really do not get where the traditional commentators are coming from. Psalm 90 opens "A prayer of Moses, the man of God"; the traditional commentators declare that this introduces a series of eleven psalms written by Moses. The problem with this is that 1 Chronicles 16 attributes a slightly corrupted form of Psalm 96 explicitly to King David. So why do the traditional commentators complicate this (the implication, presumably, being that David was quoting Moses)? Why not go with Occam's Razor, that the simplest explanation is normally right?

I suppose Psalm 95 makes reference to an incident in the life of Moses, but the Mosaic origin explanation then requires that King David changed the wording from an original "you" to "your ancestors"; Psalm 98 also refers to Moses and Aaron, but also to Samuel, requiring another purported Davidic change.