As far as I understand, TCO can't be applied in all situations so it may be risky to rely on it. If you need to rely on in (meaning that your program breaks if it's not applied, as opposed to just being a bit slower), then shouldn't the language provide a way to enforce it? That is, the language semantics specifies O(1) memory for tail recursion, for example. If it does not, you are just up for a guessing game and things will break in unexpected ways and moments.
