This is Amazon's way of handling the issue. Another option would be to cut a deal with Apple. Anyone having a free sample on their Kindle app presumably got it

This is Amazon's way of handling the issue. Another option would be to cut a deal with Apple. Anyone having a free sample on their Kindle app presumably got it from Amazon's website and knows how to buy the full version. Compare this with trying to read a Nook, iBookstore, or DRM free ePub on a Kindle Fire. I'm sure it can be done, but it's well hidden.