akerosid,
Thank you for your well-thought-out response. Exactly what I was thinking. Not all routes will support such large aircraft. You could use the 787 to fly the longer, thinner routes that would not support a 777 or A350. As an example, Continental Airlines in the States has announced that their first 787 will be serving Auckland from Houston, Texas - that is a very long route. At the end of the day, you need feed for the major hub and you need to control distribution. Perhaps you could start service with the 787, generate more demand, and then transition to a 777 or A350 down the road. That's the point.
Again, EY and QR use larger aircraft and yet they are also loading up on fuel-efficient 787s. I guess it comes down to different strategies.