There are a few reasons for the slow adoption:
- Price of the player: Even with the discounted price, all the next gen media players are incredibly expensive.
- Price of the media: HD-DVD's and Blu-Ray discs are significally more expensive than DVD's.
- Most people don't have a TV that can even take advantage of HD-DVD's or Blu-Ray.
- The selection for both is fairly shitty.
- You won't get all the new releases unless you commit to both formats.
- People don't want to commit to one format only to have it fail.
For me, I just refuse to commit to a format until there is a clear winner. Even if I had a PS3 or the HD-DVD 360 add on I still wouldn't buy either. The movies are more expensive and say, if I had the HD-DVD add on and HD-DVD's failed, I would have to keep my 360 around just to play those movies or buy them again. Either way isn't really preferable.
A little off topic, but I've noticed a fair amount of HD-DVD's that play in HD-DVD players and DVD players. I don't know if Blu-Ray does this too but if that starts to become the standard that would help sales. If I did buy HD-DVD/DVD's and HD-DVD's did fail, I wouldn't be out anything. It's nice to have that little security blanket and that would do a great amount to boost sales.
