I'm really not surprised. iTunes is not a very good deal. $1 per track is about the same price as buying a CD, give or take and the quality (of 128Kbps AAC) is not very good. If CDs are the same price I much prefer the CD. Downloads need to be priced at about 1/3 the CD price. It can be done. Check out emusic.com they sell digital tracks of better quality than iTunes for $0.25 each.
I think what's happed with iTunes is the same thing as when CDs where new. Most CDs then were "back catalog" re-releases of vinyl albums. People bought the CDs fast and then "caught up" and after that only bought a recent release now and then. I think the same has happed with iTunes. The Apple music store is mostly "back catalog"
I remember when I thought "Cool, I can get John Coltrane on CD now" and I did I have a dozen of them . But he ain't making any more records so now I have to wait for something I want to come out and it does now and then but when CDs were new there were many hundreds of CDs I wanted. Possibly it is the same with iTunes. When you buy a new iPods there are hundreds of tracks you might want, but then after you have those
Maybe an analogy. You have a tank with all the air removed, just a vacuum inside. That is like an empty iPod. You crack the valve and let air in. At first it rushes in until the pressure equalizes. After that you just get a slow exchange of air