If one of your primary motivations for working on FOSS is to improve the world (which for many of us is the case), then it's very easy to feel an obligation to un-break Amazon because it is a quick way to improve the world for millions of people.

That, on its own, is fine. It brings you satisfaction rather than financial support. What starts being fishy is when companies like Amazon who can readily afford to offer financial support instead rely on and exploit that sense of obligation to get work done for free.

I realise this sounds whiny and that's not the point. The point is that by withholding FOSS contributors financial support, these companies are creating an environment in which the best and most dedicated contributors run the risk of burning themselves out, making everyone worse for it.