Presumably, if it's a part of the arc plot, then it needs to end in a certain way - and thus the authors are more likely to write a campaign that railroads the characters into certain actions. This means that world-shaking events are not as likely to be found within a commercial campaign. Not everyone likes the same style of campaign. Some groups like dungeon-crawls. Some groups like politicking.
Some groups enjoy mysteries and puzzle-solving.
No pre-written campaign can please every group. No matter who you are, it's unlikely that your tastes will jibe completely with those of the author who wrote the campaign. Hopefully the author will have provided a decent selection of plots, or ways of accomplishing what plots there are. Still, not everyone will like every campaign. You may think the campaign suffered from a lack of politicking, but your neighbor may feel frustrated with the amount of politicking already present.