This isn't a deliberate choice though on their part, is it? Isn't it just a consequence of everyone depending on readline and readline using emacs-style key bindings?
Some Emacs-style bindings, like ^W (erase word) and ^U (erase line), are baked into the UNIX tty discipline -- basic implementations of these bindings exist within the kernel.
Although, surprisingly, most command-line interfaces and command-driven apps (like redis client and psql) use emacs key bindings for command history.