OSX already supports HDCP. The laptops support it through the minidisplay port and the mini even has an HDMI jack.
Also, despite Job's claims, Apple isn't entirely a mobile devices company. A Mac Mini with a bluray player would be rather sweet actually and use a lot less wattage when watching movies than my current PS3. It'd be a near perfect HTPC. Additionally the 27 inch iMac's screen goes to waste without the highest resolution content possible. Yes, it does make a difference on "such a small screen" since you're
sitting closer to the screen than you would with a TV and are thus better able to notice the pixels. Having it as an option on laptops isn't as important
As par benefits, perhaps it's not so much about gaining so much as keeping the ones we already have. I hate DRM just as much as anybody else since indiscriminately locking up the media in this fashion effectively kills off most applications of fair use for the afflicted media and hurts hardware compatibility/diversity. However as as Blu-ray is the media format the studios have decided upon, I'm at least partially willing to put up with any additional requirements it might impose upon OSX to preserve my interests as a customer. To me physical possession is more than just the ability to put something on the shelf, it's a proof of purchase and a form of ownership.
If the future becomes downloadable content, we can all say goodbye to
First Sale Doctrine, since DLC and the second hand market are effectively incompatible. It'd give too much censorship power to the studios, especially if we don't have control of local copies of the files, as things might happen with trusted computing platforms
similar to iOS and The Cloud. Even worse, most obscure media would be effectively lost within a generation since there'd be effectively no opportunity to rediscover the media once the original owners lost interest or died. This means no more cult classics and art made before its time, such as the
Mona Lisa, might not ever be appreciated at all.
On another note, personally I'd prefer something other than optical media, kind of like an SDHC card since it'd resolve or minimize most of the issues such as durability and space confinement. However no such alternative exists in the movie marketplace and so long as we are using the space on an optical drive like DVD, we might as well use it for whichever optical drive is best at the moment, which just so happens to be Blu-ray. Optical media also has the benefit of being very cost effective to pass around, say if you have friend/family with a dialup/metered internet connection (they do exist, esp. in more rural areas) or if you have particularly
large files to send.