The patch author does the "initial" work. But then it's up to the team to learn the patch, understand it and keep maintaining it.
Every line of code is baggage.
If there is no demand for something at the time, it makes sense for maintainers to reject that. It's up to them to maintain that patch from now on.
No one is asking them to. An open source project is not a corporation, it has no shareholders who require growth at all costs. So someone doesn't contribute to the project, if there's enough other contributors to keep it healthy then who care? No need to try and get every single potential contributor to contribute code to the project.
It's not hard.
A second, separate thought. Perhaps it's not quite as easy as you think it is, and perhaps you're not as good at it as you think you are. Case in point, the comment you just made was not exactly the nicest I've read today.
- technical: E-mail is not a particularly good medium to convey emotions (in either way). For example someone with a naturally terse communication style may be perceived as harsh, while in person he's actually a very friendly bloke. And there's no way to communicate this impression back.
- cultural: Often what is quite polite in one culture may be seen as quite impolite or even rude in another. It's not just country vs. country, but even region vs. region (like for example East Coast vs. West Coast).
- personal: People in the community may know each other pretty well, in which case the communication style may be quite a bit more direct. But others may lack the context.
It's almost impossible to get it right all the time, without resorting to entirely mechanical corporate communication style. Which is not fut at all.
Of course, this does not mean there are no truly harsh / rude / WTF posts (even on PostgreSQL lists). But I'd say most of the time it's not meant that way.