Why do people need git support in an editor so much? Using git from the terminal is easy and you always know what is executed because you do it manually.
Sublime Text can handle the former with the plugin GitGutter. Atom's branch reminder is a nice-to-have but not something that I feel is necessary, so with the plugin I'm a happy camper with Sublime.
And to answer your question, probably for the same reason why people have moved on from Assembler to C to managed memory languages to JS and to today's JS frameworks, they want to avoid the "rough" parts by adding another layer of abstraction. For some people constantly going back to the terminal looks "rough", I guess.
They've also become thousands of times more productive.
Do entire dev departments use ASM for shitting out crappy electron apps? If it wasn't for all those abstractions, a large amount of today's developers wouldn't work in software development. Show some respect for those whose shoulders you sit upon.
I am both comfortable with git on the command line and through emacs. I prefer magit mostly because of its contextual support. With the command line, each command can derive no context from the last command. With magit, it's easy to drill in and see more relevant data (or edit that data) quicker and easier.
Just wanted to point out that not everybody is merely looking for an easier experience, or one that looks prettier.