There is 'general public' and there is 'tech-savvy android users'. The former you have probably characterized correctly, but I suspect you are underestimating the size of the latter. As the grandparent mentions, if people are posting on forums to help support the devs, then at least some people are being persuaded to use the service because they believe they're helping the developers.
Many people do go out of their way to support independent musicians or indie game makers. It's not unreasonable to believe that there are people who want to help support small mobile development shops.
It is helping the developers. It is getting them a broader userbase than they would otherwise have by having it promoted front and center on the app store, and also it being free. I think it is pretty humorous people would assume they would just get free money from Amazon for this.
As these developers discovered, all a broader user base brought them was increased infrastructure and support costs, with zero uptick in subsequent sales.
"A broader userbase" that doesn't pay anything isn't "help" by any stretch of the imagination for a number of business models.
Many people do go out of their way to support independent musicians or indie game makers. It's not unreasonable to believe that there are people who want to help support small mobile development shops.