If you need to build something from source (my use-case: Vim, so I can change which language bindings exist in the resulting build) it can sometimes be a lot easier than cloning and using the "raw" C/Make build system.

Also, assuming a downstream distro like Debian or Ubuntu, what's in Homebrew is likely a more up to date package. You could fiddle with adding/using Debian testing or some PPA, or... you could just use Homebrew.

(FWIW: I use Arch and the AUR on my desktop Linux installs these days, and it's essentially the same process. But still using Homebrew on the Mac, and occasionally in Linux when I'm not on a desktop)