Even at a small-scale legitimate level, Amazon's useful as a sort of pseudo-cash/petty change bank. They're often a good way to cash out reward points of various types or as a "bank" to convert things like Visa gift cards so you don't need to keep track of them.

I have noticed though that Amazon seems to have recognized that people like them for this sort of thing and their point conversion rates often carry a bit of a premium and certainly aren't as good as you can get from some more niche retailers.