I agree--I once used a library and noticed that it was missing some functionality. The mailing list had a number of people requesting this functionality. I found an older piece of code with the functionality and updated it to the language of the library. I got license permissions from all the original authors. I submitted it and the maintainers raised some questions about code quality--but one of the maintainers thought there was a workaround and didn't really want to add it. I acted on the code quality issues and the code just sat around and was never accepted and the mailing list still (years later) has people asking for the functionality, but I'm not going to spend more time on it when it seems that outside contributions are not welcome. This was after climbing the barriers to entry of trying to figure out the layout of the project, procedures for submission, etc.

In contrast, there was another project where my student and I noticed a bug in a piece of software and patched it. It was quickly accepted and we moved on. I would be happy to contribute to that project again.

It's all about barriers to entry. If a project wants outside contributors, those barriers need to be low. Of course, the project creators/maintainers are also doing this in their free time, so have the right to do what they want, but they should expect less community contributions if they make those barriers high...