I bet you the overwhelming majority of ipod (any type) users go with the stock earbuds.
Why buy new ones when you get a free pair?
Of course, a lot of people get upgrades (i use third party ones as well) but most people don't bother. So apple probably isn't too worried about the audiophiles that use other earbuds with the shuffle. (Hell, even I use the regular apple ones with my shuffle.) That being said, the shuffle is not really an audiophile's product is it? It's just music on the go.
I dunno, I could be wrong here, but I'm sure they have done some market research that doesn't just involve reading posts on macrumors.
Exactly! The shuffle is supposed to be apples zero thrills music on the go device. Music, just music, which is probably why like someone else stated that you cant fast forward through a song (which I'm not sure of yet).