If I had a nickel for every time someone asked me "Can I get that online?" I'd be... well, not rich. Nowhere near rich, nickels just aren't worth that much. But I'd have a LOT of nickels. And I'd almost double that pile if I got another one every time I had to answer "No."
The Internet may be big, but it's only been around for a couple decades. Which means (see previous page) that there's 4980 years of human writing which was done before the internet. That's a lot of writing, and most of it's on paper. While libraries and companies are furiously scanning that stuff (much of it under deadline before it disintegrates), they're still nowhere near finishing.
Also, don't forget that many books and journals are still published only in paper, with no "e"-versions. Again, online publishing is soaring, but it has in no way replaced paper books.