Sometimes it just takes a bunch of prodding from multiple users to get a patch merged[4]. Sometimes even that isn't effective[5].
I didn't have to look hard to find these examples. I just scrolled through vim-dev looking for "patch" next to an unfamiliar name. This is a common problem with mailing lists: old things fade into oblivion whether or not they've been dealt with. Not so with GitHub's pull requests. PRs stick around until someone closes or merges them. That one difference makes it much harder for contributions to slip through the cracks.
1. https://groups.google.com/d/msg/vim_dev/iB2YYel67io/SBHYHpSM...
2. https://groups.google.com/d/msg/vim_dev/UTOY6V6UCkk/-0lqupnc...
3. https://groups.google.com/d/msg/vim_dev/0It1ZTos_QY/63Xc9NrT...
4. https://groups.google.com/d/msg/vim_dev/WeBBjkXE8H8/MRLPPMjV...
5. https://groups.google.com/d/msg/vim_dev/kG3Qaz8M9kw/YyZDzwkc...