Not beginner-friendly, it's tiny Emacs
Many argue the 'beginner-friendly' framing was wrong: atto is a minimal Emacs clone with C-x C-s style bindings, which beginners won't find intuitive.
Sized for the rescue system
Defenders note its real purpose is a 48 KB, permissively licensed editor for rescue/single-user mode, friendlier than ed or vi, which nano (GPLv3, 300 KB) and micro (Go, 11 MB) can't fill.
Console keybindings should modernise
Some want CUA shortcuts like Ctrl+S everywhere; others retort Emacs/readline bindings are a 50-year-old Unix standard.