So, you're more likely to stream current music, and more likely to buy older music, that kinda deal, etc.
Btw. I think the same effect is also present in consumption of new (or "current") and old movies. I think it's simply an effect of convenient streaming and subscription services in how those sales have shifted.
With a convenient access to music and media, I think the distinction between "current" and "catalog" is very difficult to figure out correctly, etc. Is a track that is a month old "old" or "current" - you tell me.