Having used (and loved) both Magit in Emacs and Fugitive in Vim, I totally get it. It's simply a pleasant experience to not switch contexts too far away from my editor. I certainly don't mind performing Git-related tasks in my terminal, I just like the flow provided by Atom's Git integration. At this stage in the game, it's not perf that's holding me back. Both Atom and VSCode perform well enough to be a daily driver. For me it's Atom's far superior Vim mode that keeps me using it.