I don't know what it's like in the UK, but this rings particularly true:

With nowhere to get these singles and no desire to buy an expensive CD album just for one song, it is no wonder many fans turn to file-sharing systems.

I have one thing to add, though. Even when (CD and cassette) singles were available, they cost about half what the album would cost for one song, maybe with one or two remixed versions of the same song, and then some album detritus. Or I could buy the album and take a shot at there being one more song on there that I'd like. That line of reasoning led me to the conclusion that buying the single was fiscally stupid, but I didn't have the confidence that the album would contain even one additional track. (I've always had a good ear for one-hit wonders). So I most often ended up buying nothing when I was vaguely interested only in the single (as opposed to the album). In fact, the only singles I ever bought were for albums I really liked so that I could get the B-sides.

And that all ties into price fixing. If they'd sell the damn single for $2 or $3 instead of $7, they might sell more of them, but now it may be too late, as most stores no longer carry singles since they didn't sell.