Albums are most often organized chronologically because they tell a coherent story this way. First this happened and then that happened. The story makes more sense when it is based in time. Chronological organization is easy to think. The decision about where a story goes, is already made.
Another outcome of chronologically-organized scrapbooks is that through turning the pages, the reader can learn how a the scrapbooker (or family) has progressed (most history after all, is written as the story of progress).
I wonder if the appeal of non-chronological scrapbooking comes from the fact that most of us experience very little change from year to year. Even the changes that do happen, while seemingly big at the time, are often quite small in the grand scheme of things. Just a thought. What do you think?