[rbehrends]

First of all, ebooks still make up only a fraction of the book market (especially outside the US). Most big publishers will have to support hardcover, paperback, and ebook version in parallel and price them so that they make a profit for everything combined. Hardcover and paperback versions are not going to go away anytime soon, either.

Second, publishers also make losses on books that don't sell and that they have to recover. The majority of books don't actually sell a whole lot of copies, so the fixed costs associated with producing a book can be a pretty high percentage of revenues for the average book.

Finally, publishers provide editing, translation into foreign languages or negotiation with foreign publishers (assuming your agent didn't retain translation/foreign publication rights), production, marketing, accounting and sales services, distribution, and warehousing (for dead tree books).

Note also that you can equally ask what Amazon provides with regards to ebook distribution: In the end, it's just another middleman that got a head start because it was first to market with the Kindle, but is otherwise unnecessary. In some markets, publishers selling directly to readers (on non-Kindle platforms) makes up a significant part of sales.