When I got my first iPod touch I listened to an audiobook and memorized the minute that I paused. When I listened to it again I wanted to go there by clicking on the scroll bar, but the scrollbar did not appear when I clicked on the audio file. So I had to use the forward button. To trigger the scrollbar you have to click just on the touch area in the middle, but I hadn't known this at the beginning.

I think it is not their focus, because normally you don't go to another minute in a song. You'd rather go to the next song. So you don't need the scrollbar often. But when you need it, you are supposed to know how to trigger it.