Where possible, I try not to focus on negative motives. Quite simply, if people see a benefit in DRM-free, why not expect them to pay for it? And there are other platforms beside the two I mentioned – it’s not a choice between DRM-free and (for better or for worse) Amazon.

In case your question was not rhetorical: to folks like me, I view DRM as abuse, because it inevitably leads to me paying for something that I won't end up being able to access down the line. It is in direct conflict with building a library. Having the author opt-in to applying DRM to their books (as you have on Amazon and Google Play, for example) and then expected me to pay them extra so I can actually own the thing I paid for makes me take three steps back from the "Buy" button. I tend to just walk out rather than be treated that way. As a result, I've stopped buying Amazon Kindle books entirely (now that I can't strip the DRM). If I'm paying the money, I'm going to demand control, and if I can't get that control, there will be no transaction.

FWIW, LeanPub for your book suggests $25, and the DRM-laden version is $13.50. That's quite the premium!