Ditto. I've been an Amazon user since the late 90s. They've got an incredible amount of user data about me, including wishlists with thousands of items. That all ends about two years ago. This is when I started buying digital books on my wife's account.
She's not much of an Amazon user, but I bought her a Kindle as a gift first, so...we already had a bunch of digital books attached to her account. So now Amazon has a lot of data about a sort of split personality woman who likes anthropology, travel, cooking, etc. as well as math, programming, photography, etc. This is a massive fail and a loss to Amazon in my mind.
The reason I don't want to buy two of everything, aside from the obvious fact that I don't do this in the real world (i.e., physical books), is that I don't expect these copies to be valid in 10 years. Any DRM-based data is likely to become invalid over time unless it's eventually stripped. Why would I pay twice for that? In addition, it's lower fidelity than the physical book or an equivalent PDF. So I'll probably have to buy it again anyway.
Apple figured this out and now sells MP3s and, ironically, Amazon also sells DRM-free MP3s. I'm sure they're trying to bring publishers into the 21st century. They're just not doing it very well yet.