It's not so much that mutation was added to racket. Racket started as a scheme, which has mutation. Some of that, like set-car! and set-cdr! were removed (con

It's not so much that mutation was added to racket. Racket started as a scheme, which has mutation. Some of that, like set-car! and set-cdr! were removed (cons cells were made immutable, though mcons was added for mutable cons cells) set! is one wasn't removed. I think removing set! would constitute a much more radical departure from scheme than what's been done already.