Why isn't battery life a priority of the Nexus program?

I'm using a Nexus 4 as we speak and will try out the Nexus 5, but based on my experience with the N4 and the reviews of the N5 it seems like we have another year of battery disappointment.

Obviously 2300mAh and KitKat optimizations are not enough to provide Droid Maxx/ LG G2 level battery life with the Snapdragon 800 processor.

Would a 2600mAh or greater battery really have made the phone that much thicker/heavier?

Battery life is the most important feature for me assuming build quality, screen, OS are within reason.

Based on what I read, many others agree. I don't get why Google is still chasing thinness at the sake of battery life.

Maybe next year. Sigh...