So the whole topic is not terribly hard to understand. When you see

    return f(x', y', z')

in some function g, then g's stack frame just describes a forwarding proxy, “let me take the value returned by f and hand it to whoever called me.” And like with all forwarding proxies you can just delete the middleman and it works fine. You would do this because it gives you an alternate, debatably simpler, model for looping. In other loops you either have to return out midloop, or have to explicitly marshal your inputs and outputs of each step into mutable variables, see. So here is the same loop written two ways, the second is probably less familiar to you:

    function fib(n) {
      let curr=0, last=1;
      for (let i = 0, i < n; i++) {
        [ curr, last ] = [curr + last, curr];
      }
      return curr;
    }

    function fib(n, i=0, curr=0, last=1) {
      if (n == i) return curr;
      return fib(n, i + 1, curr + last, curr);
    }

These are only different styles for the same thing if you can trust that the call stack does not overflow in the second, which it doesn't have to because it returns a call to a function. So the problem is, if you have too many forwarding proxies in a chain, the language gives up on you.

Guido gives four reasons, you are quoting the first. The counterpoint there is, tail calls are just rewrites for looping constructs, as Guido admits in point 3. Should we ban loops as not “maximally helpful for debugging” because not every iteration appears on error stack frames? Perish the thought!

So at the end of the day that one just turns out to be, I am a lazy developer and don't want to figure out how to track this looping info in a way that makes sense outside of the call stack, the call stack exists and works, let's just keep it. And like, that's respectable!

The other 3 reasons are better? Reason 2 is correct, Python has multiple implementations and they'd all have to play, cf. the OP where JS implementations didn't. Reason 3 is correct but unimaginative, there's no reason you can't write a loop in this style and use Python's data structures, for that matter you can write in this style and not use any data structures, like the example above! Because the technical objection isn't really there, again, this boils down to just, Guido wants to read Python code and he finds recursion hard to read, and wants the language to make it deliberately slow so that he never has to read it. That one is valid, but it sounds almost borderline unethical? And I will admit that reason 4 fooled me at first! This appears to be a damning problem but in fact it's just smoke and mirrors, right? “I might not know who the forwarding proxy is forwarding in advance.” Yes that's true but we can agree that the forwarding proxy is unnecessary no matter what it is forwarding. Sure, your language sucks at referential transparency, but if you are conflating these two things you are confusing the issue, no?

Okay, so I started out this comment wanting to defend Guido and here I am at the end disagreeing with him...