It's a matter of cost and time to market. Blue Ray requires new manufacturing processes and new replication equipment. That's a rather sizable investment to make and it's going to take time to deploy. And maybe they don't want to pay big $$$'s to Sony to use the technology.

HD-DVD can use existing processes and equipment (as you pointed out by switching in 15 minutes). Advances with compression technology make the difference between 15GB/layer (for HD-DVD) and 27GB/Layer (Blue Ray) much less important, and with the advent of combined HD-DVD/DVD you can market the aspect that you're preserving the customer investment in DVD purchases. As a potential customer I think I'd be more willing to buy a HD-DVD/DVD even though I may not currently have a HD-DVD player (or HD TV), knowing that when I do eventually get a player/TV, I'l be able to enjoy the HD content, while still being able to enjoy the DVD content on my existing player and 4:3 TV. Blue Ray doesn't offer anyway to preserve my DVD purchase investment and requires that I purchase at least a new player (hopefully capable of playing both blue and red formats).

--Scott