Rightly so, considering the next step for a lot of such OSS projects is AWS offering it as paid hosted service with zero benefit to the maintainers. So then they have to couple it with a restrictive license which devalues the "open" part.
- benologist, https://news.ycombinator.com/item?id=17454032
If AWS wants to copy you, not having your source code isn't going to stop them.
Why do they have to?
If it's really critical, you'll do that but a company has to be really dependent on a piece of software (or unusually cognizant of the open source maintainership problem) to go the second route. Built-in defaults carry a lot of weight.