Thanks for the review, Tom!
A few quick comments:
1. Duplicate blank maps. One of the things Andrew wanted to do with the design of the map sets was to minimize the investment required by a group wanting to play a campaign. With this in mind, he broke the maps into 6 sets of six maps each such that every single map in each set could be built from a single Battleground Terrain Pack. The reason each set has a blank map is not so that there are more blanks than anything else but rather so that every set has one open plain field.
2. Time commitment. Most campaigns we know of are being run on a one-game-per-week basis. That's still mainly for pretty serious players (i.e. those who have a weekly game night and are happy dedicating a couple of months of it to Battleground) but the "full campaign in a weekend" is for exceptional situations like a game convention and die-hard fans.

3. More maps and scenarios. Andrew has been adding new content for Kingdoms every month. So far he's added a choose-your-own-adventure style campaign between the Lizardmen and the High Elves, a 7th set of maps and some modified scenario cards with different victory conditions to increase the likelihood of decisive results.