More importantly they are familiar intimately to those active in the field. And often reflect an underlying ideas that are useful in the field. People often wr

More importantly they are familiar intimately to those active in the field. And often reflect an underlying ideas that are useful in the field. People often write equations out in full and marvel at the ludicrous clunkiness of it all. Usually because they expect that will help them understand a concept. That doesn't work. The notation often suggests a manner of thinking about an idea that is more useful than seeing the idea spelled out. Of course you probably should have spent some time peering into the blackbox of notation and physicists are probably most notorious for not caring to.