I can then drill down to each file with the visual diff and see whether the changes are something I want to check in, or just debugging. If it's debugging code, I can click "Discard Changes" to drop all changes I've made to that file. Or I can selectively discard a hunk or discard lines.
When I show these features to command line purists, they always concede that this can't easily be done with the command line. So I don't see what's to gain if I'm losing those features, which I rely on constantly.
I've been working in SourceTree for a decade, so I know all the quirks by now, which I pass on to any new devs who want to use it.