Apple makes very little money off iTunes video sales and it's doubtful the lack of a BR drive does anything to increase their video sales. Who buys a $20-$30 BR, realizes they can't watch it on their Mac, and instead buys it off iTunes? Who wants a movie and says gee -- I'd rather buy this off iTunes instead of playing it on my 60" 1080P TV with a $99 BluRay player connected to it. Doesn't make sense at all.
I think they just realize few people actually want to watch BR movies on their computer. Spending $X per computer to enable it (software/hardware) doesn't make much sense. It won't increase Mac sales much. It's just flushing money down the toilet.
Most people will not use the IMac as a primary Blu-Ray player, Agreed, most will use their $99 Blu-Ray or Sony PS3 or whatever on a large 1080P TV. But a 27" IMac makes a great secondary BR player for your bedroom, etc. Really large programs like newer video games that need several DVDs or a crapload of CDs can now be copied from a single Blu-Ray disc. Blu-Ray discs can be used to back up your hard drive, won't use as much discs as DVDs. There are online backup options but some prefer having backups physically available.
I agree that adding Blu-Ray may not significantly increase MAC sales, but considering that video chip and display technology on the MAC make it possible to view Blu-ray and Apple continues to keep up with the latest on video and display technology it doesn't make sense to keep using DVD, a 15 year old technology as a video source and optical drive. The costs of Blu-ray hardware is at the point that it costs the same as DVD hardware 10 years ago when Apple started selling its DVD based Superdrive. As for coding issues, as I've said before, Apple has the resources and smarts to overcome this. I think Apple wanting people to use the Apple Store as the primary source for HD material will eventually be to Apple's disadvantage the way AT&T is for the IPhone. People want their options and Blu-Ray is another option that is available right now.
If Apple really wants everyone to use the Apple Store as a primary means to obtain software , video, etc. I say they should remove the optical drive completely. For instance, you can no longer buy a disc for your MAC OS X Snow Leopard upgrade. It only can be downloaded and every other piece of software that goes into your MAC can't be installed by disc you will need to purchase, download and install from the Apple Store. How's that for a solution? Why not? since software can now be downloaded. Why copy photos on a CD of the kids for grandma since she can get it remotely online. Pull the trigger Apple remove all optical drives!
Oh I forgot to add. You can now install SSDs on your Mac. But you still need to use 15 year old DVD technology on your Superdrive. Sorry had to let that one out...