Nowadays I just run `brew update; brew upgrade` and everything gets updated, including casks.
I'd hazard a guess that Chrome alone would put that figure near 100%
The whole malicious compliance shebang. EU mandates browser choice, so Apple implements new technological measures to ensure that browser choice will still not be offered outside the EU
brew update; brew upgrade; brew cleanup; brew doctor buucbrew update && brew upgrade && brew cleanup && brew autoremove
Edit: Obviously for users not familiar with command line programs brew isn't that "easy". But for command line people this setup is quite nice.