Local style

How useful is a newspaper's local style, anyway? In transfering from the Tribune to the Republic, I've noticed the differences in local style between the two papers and also how often it can be confusing and unnecessary. How often do people notice local style rules, and even when they do, it's usually because it has differed from other news outlets (at least in my experience). Do these differences add anything or do they serve to simply make stories more confusing and copy editors feel important in formatting stories according to these rules? I'm not sure, but it seems like there can be a uniform way to do things, and it seems that way should be Associated Press style. For example, the Republic capitalizes "Black" and "White" when they refer to races. The Tribune and AP do not cap them. The Republic hyphenates any and every compound modifier and AP doesn't hyphenate ones where it is obvious what is being modified. Those are just a few instances where local style differs, and those differences can end up confusing the reader as they try to adapt to changing format styles.