Thanks for your feedback.
Sorry about the confusion -- EPUB & Kindle are bundled together as a package and right now you can get both formats for only $6 per book if you'd like those formats.
I have hundreds of physical books on my shelf - unfortunately, Amazon and other publishers didn't give me the digital formats free of charge when they were released.
I knew what I was buying when I made the original purchase and I was happy with my decision at the time. If a company gave me free stuff months or years after my purchase it because of a new format that would be an unexpected bonus - but I would never expect or demand it retroactively.
It's pay for convenience. If I buy a hardcover, I still have to pay extra if I decide that I want the convenience of the audiobook format a few days/weeks or months later. If you bought the PDF and now want the convenience of having the book accessible on your iPhone a few months after your initial purchase, then there's an small extra cost for that as well.