I don't think there's any definitive proof of what SQEX intentions with these releases are. There are a number of theories, some of them being:
- Cheaper to produce 1 bluray disc than 4+ CDs
- Fits more music (FFXHD not so much an issue, FFXIV however has over 6 hours of music on theirs)
- Allows extra content to be added (All the blurays I've ripped to date have had some really beautiful images that play when the tracks do. Not sure if they are from artbooks, the actual game, completely new or what. Some of them have bonus FMVs)
- Some ... interesting thematic indexing for menus, where they can group tracks together by type, like Battle, Field etc. One of them has a really neat menu that reminded me of the FFXIII talent thing.
- Is somewhat more of a collectible item
However, all that being said, if you put the Bluray disc in your PS3 or PS4, there is an option in the menu that turns the PS3 into a temporary web host and allows you to download zip files to any PC connected on your network that contain mp3s of what's on the disc. They are 320 kbps.
You can also rip the discs if you're comfortable enough with software. You have to first rip the Bluray into a container, then take the audio out of the container, then convert the audio from 96/24 to 44.1/16 since it's pretty pointless (and not mastered properly, more on that in a sec). I don't normally like to advertise here (Adam, feel free to edit this if you don't want it posted) but I've already done this for all of the FF blurays, you can download them from gamemp3s.
Alllll that being said, some of these have some serious, serious issues. You can view the threads for the albums over on the vgmdb forums for each. SQEX is doing a really shitty job mastering these. tldr of it is that they're upsampling 44.1/16 to 96/24 for these releases so a lot of them have some tracks that have really, really, really bad clipping and they sound AWFUL. It's generally on the loud/full tracks and not that noticeable on all but if you have good equipment you will notice. They've been getting better but they are still by no means that great.