I think part of the problem is the connotation of what makes a good layer. Some birds lay seasonally, or even at their most prolific only every few days. To my mind those are not good layers, because even under the best of circumstances they do not lay regularly. Birds that lay regularly, but go through bouts of broodiness when they don't lay are a whole 'nother kettle of fish.
Some people simply want the statistic of the average number of eggs per year. In my mind that tells only part of the story.