Given the limitations in the current WGT lobby system, it could be several things. Maybe they don't like the course or the shot clock settings of the game, or maybe they don't want to play against the people who are already in the game because of their tier or average score. There is a lot of room for improvement in the system to avoid these kinds of situations, but as it is, players who are picky about courses or opponents will often be put into games they don't want to play. There is very little chance that when people decline that it is anything personal.