Call stacks are almost always used in implementations of functional languages as well, even those that support first-class continuations. Even implementations t

Call stacks are almost always used in implementations of functional languages as well, even those that support first-class continuations. Even implementations that use CPS as you describe don't necessarily lose call-stack discipline (e.g. guile); that's a separate choice that some (e.g. SML/NJ) choose to make. The call stack provides very cache-friendly and gc-friendly memory. It's still a very useful construct in functional languages.