Correct, the 1.7.12.4 (Apple Git-37) does not come with gitk. You can install a more recent version of Git + git-ui as a separate formula by using Homebrew (executable brew). More thorough instructions are located on The fastest and easiest way to install Ruby on a Mac in 2022 (see this commit extracting git-gui/gitk into its own formula: git-gui: split from git formula.)
Run the following commands at the terminal:
brew update
brew install git
brew install git-gui
If you get an error indicating it could not link Git, then you may need to change permissions/owners of the files it mentions.
Once completed, run:
type -a git
And make sure it shows:
/usr/local/bin/git
If it does not, run:
brew doctor
And make the path change to put /usr/local/bin earlier in the path. Now, gitk should be on your path (along with an updated version of Git).