I use it. Mostly just love of the game. Occasionally I’ve played with custom kernel patches and custom patches to software packages, and Gentoo makes that super easy. Building software that doesn’t have a package is also pretty comparatively easy.

There’s a lot more configurability than even arch; if you’re careful it’s not too hard to get your base RAM usage down super low (50MB to 100MB range). It doesn’t force you to use any particular init system, if that matters to you. Even some individual applications can be smaller/a bit more efficient if you compile without features you don’t need. You can also keep things super up to date, run the latest kernel etc. Supposedly the Google Chromebook os is originally based on Gentoo because of the degree of configurability.

Most of those things don’t really matter, and aren’t truely unique to Gentoo, but if you were really only concerned about practicality you’d just run Fedora or Debian.

There are also a few use cases like cross building to weird hardware that other distros don’t have builds for where Gentoo can be a bit easier than LFS. Doing weird stuff like using musl instead of glibc is also possible. I haven’t heard of that on another distro (although I haven’t looked in a while).

It’s not that much harder than Arch was back in the day, which was never really that hard if you were willing to actually read the manual.

When I first installed Gentoo, it was because it was one of only around three distros that supported x86_64 at the time. Yes, that was a long time ago.

I’ve kept it as a daily driver for a number of reasons. First, because I’m a control freak, and Gentoo goes out of its way to allow me to select exactly the packages I want, and gives me access to all the knobs and switches that other distros may hide in the name of user-friendliness.

Second, because once installed it’s surprisingly solid and trouble-free—Portage is an excellent (if slow) package manager that, judging from what I’ve heard from people running other distros, is better than the average at preventing breakage, and since it’s rolling-release there are no whole-distro upgrades to complicate things. I ran one system on rolling updates for 17 years without reinstalling, and it was still pretty much up-to-date on all packages when I retired it back in March—try that with Ubuntu. (The replacement system also runs Gentoo.)

Thirdly, I’ve been with Gentoo for so long that I know how to create packages, unbork a system that I’ve messed up by doing something really stupid, and various other tricks. If I went to another distro, I’d have to relearn much of that from scratch.

(A fourth reason for some might be that it supports a wider range of CPU architectures than any other distro except possibly Debian.)