WOW, what a good argument you have there Mek. You REALLY dont know shit about Rangers or Celtic do you...
The historical background, the religious nature of both clubs, the history of violence. THAT is why the Old Firm games are BIG games, and that is even before the fact that most seasons both clubs are fighting each other to win the league and the points gained could win it for them.
We have played each other that number of times because the league is different in this country and the top 6 teams play each other 4 times, and have a good change of playing each other in cup competitions. Yes, the league structure is a pile of crap, but what are you going to do?