Random perspectives from Cleveland

Why does the NFL have any plays that cannot be reviewed? It's so stupid. Two plays that were actually fumbles were called as "player down by contact" which is a non-reviewable play. Why is it non-reviewable? Is there a purpose to that? Shouldn't the goal always to be to make the right call? Who cares if the game takes 6 hours if all the calls were correct. I'd rather have a 6 hour game with no blown calls than a 3 hours game that was decided by the refs instead of the players.