It just really highlights how much better BitKeeper and then Git's design was compared to what came before. You then pile on being free/OSS, and being "proven" by an extremely large, well known, and successful project on top, and you have yourself explosive growth.
There are developers around these days who never had the displeasure of using the pre-Git source control offerings; it was rough.
Of course, `git send-email` has a plethora of options, e.g. you'd typically add a cover letter for a patch set.
Also, in the Linux kernel tree, there are some additional helper scripts that you might want to run first, like `checkpatch.pl` for some basic sanity checks and `get_maintainer.pl` that tells you the relevant maintainers for the code your patch set touches, so you can add them to `--cc`.
The patches are reviewed/discussed on the mailing list that you sent them to.
On the receiving side, as a maintainer, you'd use `git am` (apply mail) that can import the commits from a set of mbox files into your local git tree.
> ...and I immediately got flamed by several people because no one used patches any more.
How are these ideas connected? The intent of git is that you work with patches.
Unlike patches, pull requests aren't even a feature of git.