There are basically 2 types of coders around on vB.org (using coders as example, but same applies to Designers).
And then there's the hybrids.
To date I've done 14 major hacks for vBulletin - only one was released on vB.org and I've only taken 1 paid request from here. There's a myriad of reasons why I don't release/don't take paid jobs but I'll give the most prevalent:
A mod I've done "for fun" may have no value outside of a specific type of community
A mod I've done may be for a paid customer and cannot be released
A mod I've done may have some sort of proprietary technology that I cannot legally release due to NDAs
A person may be requesting a mod that will take me a month to complete (with my current workload) and 20,000 lines of code and is offering $100 for it.
Anything I release to vB.org will be marked as "supported" - but if it's a free mod that I've done it's very last priority - the projects that pay the bills are prioritized first (I do vB hacks/other web projects for a company as a job). It doesn't mean I'll ignore it - but it also means I can't guarantee a 48 hour turnaround for bugfixes. If I had more free time, however, you'd probably see more "freebies" pop up from me here as I do enjoy it and like giving back to the community when I have time. After all, I'm a self-taught C/PHP developer and Linux admin and I learned by watching what everyone else did and then taking it to the next level =]