well, supposedly they "can" do it (at least with iTunes 4.8). unfortunately, all it really prints is booklet with a cover and a playlist printed over a ghosted image of the cover. full album art, while being a shitpile of work to play catch-up on, would often be pretty prohibitive for consumers to print and paste-up into replicas of the store-bought cds.

imagine printing pearl jam's ten, or that godforsaken radiohead kidA thing. they could provide a pdf of anything, but i'm betting they compare the cost of providing the pdfs versus the amount of times the pdfs are downloaded and just not bother. there's really minimal demand, considering that the selling point of the mp3 is compactness, and jewel cases inserts are often anything but.