Stripping the DRM for most drm (adobe or amazon) is way easier than you seem to think. Digitizing a print copy...

- usually costs more to buy

- takes much more time to dissect and scan the book than it takes to crack drm

- PDFs (from scan) have lower visual quality, and are bigger (PDFs have a place... it's difficult to convert something like an organic chem textbook with all the margin diagrams and complex layout into a nice epub, for instance, but even then good PDFs are generated by the publisher, not scanned)

- OCR errors, so text search may not always work even if you can read the original text (you kept is as a pdf, kept it as an image with OCR text as a separate layer only used for searching, or used cleartype-like tech which is similar but basically compresses similar looking glyphs)

- converting to a real ebook (epub) for reading on smaller devices, without extensive proofing (and reformatting if the book uses layout, as in it isn't a traditional fiction/nonfiction work that's all uniform prose), has mediocre-to-horrible results. Line wrapping, layout and OCR errors abound.

Why not just buy a digital version and remove the DRM? It's easy enough and almost always cheaper.

Not all books have a digital, DRM free version? Also, sometimes having the physical book is nice, especially for quick reference between a few known pages

Because that gives money to encourage more DRM.

although it does not make sense, I believe it is illegal to remove DRM...

That's under the DMCA's no circumvention clause (in the US at least). It may not be illegal in other jurisdictions.

Interesting that the DMCA essentially slapped fair use squarely across the face.

Out of curiosity, what kind of scanner do you have?

I've been wanting to scan all my important mail and documents for a while, but I need the process to be as frictionless as possible for me to actually go through with it and I'm unsure what kind of scanner to buy for that.