www is just the easily visible part of the internet that everyone could access. Usenet, BBS, email etc are all non-www parts of the internet that were more important in its early history but harder to access because you couldn't just point one program at them. www just happened to evolve fast enough that it could emulate the old layers, e.g. Hotmail is the thing that kept emails alive past 1995. I'm sure that without a www front end email would have gone the way of gopher.
