> Well, we’re paying our affiliates 5% for referrals. If we pay charities a tenth of that and call it a donation, it’ll be great PR and we’ll also make a profit on every sale because we won’t need to pay a full commission…”

This is a very good point. When a customer goes to the Smile URL it supersedes whatever other referral link they might have come through, or might be lingering from a prior search/click. Given this framing, it's hard to understand why they would have eliminated it. My uninformed guess is this is about simplicity and saying 'no' to things that are not core to the business. This is something that makes money, but after factoring in the dev time that goes into it, the total incremental revenue is probably not large enough to justify. Amazon says 'no' to lots of new things that would generate revenue, so at some point it makes sense to cut existing programs that aren't making a big enough impact.