Nobody contends that it's your decision to give away your book, but you simply cannot avoid this. It was tried with music and it failed, it was tried with movies and it failed.
There's a pattern however.
The harder something is to find, the more perceived value it has. For example the iTunes store is only somewhat harder to find than just searching google. However if all you know about a song is a couple of lyrics, you might enter the lyrics you know into google, it will find a "unauthorized copy" of the lyrics from which you can find the title and hopefully the author, and then go to itunes and search it. It might not be on iTunes in your country, so you then have to go back to google and see if Amazon shows up. If Amazon doesn't show up, now your choices are buy/pirate it DRM-free from Russia, or fly to a country that has it and buy a physical CD, and hope it doesn't get confiscated by customs on the way back.
eBooks are the hardest to find, next to music, and then images. Mainly because these are DRM-locked, or not in a computer-readable format that google can search. If you don't have the title and author, you'll never figure out what to buy, and you're not going to buy 20 some items that sound like it might be correct at full price just to figure out which one is the correct one.
And instead of taking a flight to foreign country just to buy a CD that isn't sold in your country, you might find foreign store in that country that is willing to ship it to you, but you'll still risk the item being confiscated or excessive taxes added at customs.
People will prefer the easiest and cheapest option every time. You want that cheapest option to be either iTunes or Amazon, not the pirate sites. If your content isn't available on every countries version of the iTunes store, then you are choosing to leave money on the table. Amazon is a bit more flexible, and you can generally buy from the foreign site (and ship to the US.) In the case of eBooks, there should be no shipping at all.
But this is not always the case.
eBooks and music will generally play on all future devices, if they are DRM-free. Games and Software will not play on future devices, DRM-free or not. As we've learned from all software released on physical media, if the company goes out of business, or is bought/merged with another, all the old content may be destroyed with there not being any possibility of recovery. So if there is only a DRM'd version of X application, music, video, game, or ebook, and that company has gone out of business, that content ceases to exist in 120 years, and does not become public domain. Because in 120 years, todays iPad and Kindle's won't exist.
Case in point, all the old forms of electronic DRM have to be cracked in order to play a 20 year old game on a modern computer, because they run inside virtual machines that don't have the physical media anymore. Soft DRM like code wheels and "find word X on page Y in the manual" are worked around by simply copying the soft DRM with it. There are some games that may never work on a modern computer because the DRM at the time was too tightly integrated with the old assumed operating system and hardware, and the only way around it is to strip the DRM from the game and then patch the game to work on newer operating systems. (Games by Origin Systems/Electronic Arts and Sierra Online/CUC/Vivendi/Activision released between 1994 and 1999 have no source code to make their old games work on new computers, and the games that have been made to work, are the DOS versions, using Dosbox. These companies have been merged over and over again, and the chances of the software being "Remade" by the IP holder is zero.)
Businesses are frequently so short-sighted that they only care about the profits they make in the current quarter, and not any potential future profits from selling the product perpetually. If they release things with DRM on day zero just to thwart the pirates, fine. But when version 1.1 or a half a year goes by, release it DRM-free so that everyone else with a capable device can also read, listen, watch or play it.
If you don't ever release a DRM-free version, you won't get people buying the same copy every time a new piece of hardware comes out, no you'll just have people hanging on to their old hardware till it bites the dust. If you are a hardware company like Apple, getting everything DRM-free is in your best interests to ensure future hardware sales.
TL;DNR version: DRM is a short term prospect that should be abandoned once short term profits have been had in order to ensure long term profits.