Why? Because I don't really get rid of them. I remove them from my device, but they're still mine. They exist on the "cloud". Whether it's the Apple Cloud for my iBooks, or the ones for Kindle or Kobo, they are still there.
When I first got my iPad (as an awesome gift from my husband), the first thing I did was get the iBooks app and start downloading all the free classics that I've always wanted to read. For the classics I couldn't find, I downloaded the Kindle and Kobo apps and started searching. I just HAD to have them. I spent a lot of time doing this. Then, I became a searcher for Kindle and Kobo book deals. I downloaded a lot of free books that I still haven't read. I also found it difficult to resist ebooks deals, especially on books that I had my eye on previously. Soon, about 1/3 of the memory on my iPad was books. Eventually this became a problem.
I realized that most (not quite all) books I had in my eReading apps would be saved to a cloud. First, I only deleted books I'd read from my device. Then as my memory problem worsened, I deleted the books that I knew I wasn't likely to read soon. It was so easy. I just had to pay attention to whether the book would be saved on the cloud or not, because there are a few, for whatever reason, that will not save to the cloud; if I delete them, they will be gone forever. I also don't typically delete books that I've paid money for. Two reasons: I feel like if I've paid for them, I might read them soon and don't want to wait for the downloading; and because I've paid money for them, I don't want to risk them getting lost, though I know logically that it won't happen.
Print books don't have a cloud. If I get rid of them, I can't easily get them back if I suddenly decide I want to read them. If I get rid of a print book, I have to be sure that I will not ever want to grab a hold of it again. There can't be even a remote possibility of me wanting to read it again. Though my bookshelves are [severely] overcrowded, I can get more shelves for much less than an iPad with a bigger memory. Also, print books are so much prettier to look at. I don't see my eBookshelves unless I open the app, then I only see the books that belong to the specific app AND I have to scroll through them instead of just stepping back and staring. I very much enjoy have both ebooks and print books, I think I will always enjoy having both. Culling eBooks is just easier.
Print books don't have a cloud. If I get rid of them, I can't easily get them back if I suddenly decide I want to read them. If I get rid of a print book, I have to be sure that I will not ever want to grab a hold of it again. There can't be even a remote possibility of me wanting to read it again. Though my bookshelves are [severely] overcrowded, I can get more shelves for much less than an iPad with a bigger memory. Also, print books are so much prettier to look at. I don't see my eBookshelves unless I open the app, then I only see the books that belong to the specific app AND I have to scroll through them instead of just stepping back and staring. I very much enjoy have both ebooks and print books, I think I will always enjoy having both. Culling eBooks is just easier.