Right, I'm familiar with them, but a huge part of the benefit of docker is that it's basically a cross-distro (and, to some degree, cross-platform) very up-to-date server-oriented package manager. There are some efforts to create something like that for Jails but AFAIK none of them have gotten very far. Docker's benefit is that ~everyone uses it so there's usually an official docker image for anything one might want to run, kept in step with releases, plus a substantial history of images for rollbacks and testing and such.

It turns "how do I install and run this?" from a bunch of platform- and distro-specific instructions into `docker-compose up` for everything, with the bonus that the compose file also tells you exactly where data & config for the service live, so it's also concise, guaranteed-accurate, and extremely useful documentation. Old LTS Ubuntu? Can run the same version of a service, with the same command, as on bleeding-edge Arch. On Arch, exact same command. Debian, Red Hat? Same command. MacOS, if you've got docker set up, same command. Windows, ditto. The latter two, non-natively, sure, but it works. Learn docker, and you can use it everywhere, unlike becoming proficient with, say, dpkg/apt or portage or pacman. It can even kinda save you from having to worry about how a given platform's init system and process management works, at least for simple use cases.

Again, if you're doing most or everything on FreeBSD, development and hosting both, those benefits mostly vanish. But the reality is many workplaces or even personal dev+hosting environments are mixed, and docker suits those better than anything else I'm aware of—but if FreeBSD is in the mix, it's the odd-man-out. It's good not (only) because of its kinda-Jails-like isolation, but because of the excellent coverage of the image repository.