Hello Mrs. Pooky & welcome to MobileRead. As you've already discovered, it is frequented by some knowledgeable and {generally} nice people.
I'm one of those folks who own both a Kindle and a Sony reader. I try to buy multiformat books -- without DRM -- when I can get them. All of Baen's books are offered in multiple formats (and your purchase of the book entitles you to
all formats, not just one). Selected titles at Fictionwise are available in multiformat. As others have pointed out the publishers choose whether or not to use DRM on the electronic versions of their books. I'd bet that in many cases, they really haven't thought all that much about it -- they just went along with someone's suggestions ages ago and haven't reviewed the policy since. After all, books are selling, right? And the eBook market is just too small to get their attention.
One slight correction -- your PRS-700 has a
frontlight, not a backlight.
So welcome to MobileRead. I'm glad you were able to work out your format conversion so you could read the book you bought.