TL;DR - habit. Long answer: When I got myself a Mac (October 2013), I looked for a way to install software, and I was given the advice "use MacPorts or Homebre

TL;DR - habit. Long answer: When I got myself a Mac (October 2013), I looked for a way to install software, and I was given the advice "use MacPorts or Homebrew, either is fine". So I briefly looked at both and for some reason stuck with MacPorts. I have not had any trouble with it, so I never had a reason so reconsider. I think the main reason I preferred MacPorts back then was that it creates its own folder hierarchy for installed software (/opt/local), while Homebrew defaulted to /usr/local. I sometimes will install stuff straight from source, which typically ends up in /usr/local, and not having anything else live there made it easier for me to keep track.