The point is that public VCS doesn't benefit Wietse, and by extension Postfix, so why should he have one? A public VCS only benefits other people, most of whom aren't even contributing to Postfix development.
Postgres is a different project and they no doubt see a different cost/benefit ratio for public VCS, probably because they have many more core developers and contributors than Postfix.
I've actually had a patch accepted to Postfix and while I found it inconvenient not to use my usual VCS-based workflow, I also realized that the Postfix world revolves around Wietse, not me, and as a user of Postfix I benefit most when the project is optimized for him and not other people.
Postgres is a different project and they no doubt see a different cost/benefit ratio for public VCS, probably because they have many more core developers and contributors than Postfix.
I've actually had a patch accepted to Postfix and while I found it inconvenient not to use my usual VCS-based workflow, I also realized that the Postfix world revolves around Wietse, not me, and as a user of Postfix I benefit most when the project is optimized for him and not other people.