Well .... the fact is that they are being made into ebooks and distributed, just not with the authors permission. There is not enough demand from the public yet for publishers to consider it worth their while to put out electronic copies of books instead of the real thing.
I have seen a slow progression towards that though, for instance ... Roleplaying Game books are towards the expensive end of what you would pay for a book, and as such they are heavily pirated on the internet. The major companies are now starting to do simultaneous pdf releases along with hardcopy releases, as a way of combatting piracy. As we move further into the digital age I would expect to see something similar in the mainstream publishing industry as well. I wouldnt think you would lose 'real' books for a few decades yet, because of the huge attachment people have to them, but I imagine they will become rarer.
Piracy will soon become a problem though. For instance, I have come across a website that offers download of pdf versions of all six Harry Potter books. I didnt download them, in fact i have about two or three copies of each book anyway, but I can see that people would. Give it a few years, and authorised ebooks will probably have become much more popular.
Phil