Edit: here's a possibly better response than the "do it yourself" response:
XXX is a free and open source project. That means the developers put in the majority of their time on the issues that they want and enjoy coding the most, even if other good features are left out. If you're unable to help out with coding yourself, you could look through the open and closed issues and see of others have thought about your feature request too. If an open issue exists, a short "while I don't have the ability to code this, I'd like this feature too," added to the list would let the developers gauge interest and may sway someone into giving it a try. Thanks.
Edit 2: It's a bit long. This sentiment but shorter.