Those are good examples that support your point, at least about some of the music. I just tried looking for them, and you're right - it doesn't look like you can get individual tracks, and even the CDs are hard to track down, or expensive. (All Celtic Music does have the Cran CD for about $15, but then there's the shipping cost as well.)

I think the situation is that there actualy is a lot available in track form in a general sense, for someone who's just trying to build a library in a particular genre. But if you're looking for specific items, you may not find them. They may show up eventually though - I just got a CD version (and eMusic just got the downloads as well) of a favorite Welsh album I own in LP form. I had assumed it was permanently out of print, so it was a nice surprise when it suddenly surfaced in digital form. It happens.

Sorry I can't be of more help.