I am not sure there is any killer feature that you cannot do in a cli application. It is just a different way of working. Slightly better at some things slightly worst at others. But the biggest difference is what you are used to more then and single feature set.

Though I don't personally use them, I also use a shell with a lot more interactive features built in then default bash does. If I where stuck with only default bash maybe I would lean more towards them. But that is just the way I work, others work differently then ai do.