[smabie]

I'm not sure exactly what you mean by iterators, but I agree that TCO isn't that important. Like you said, most of FP is the traversal of collections. Map, scan, and foldr/foldl should be sufficient to solve the vast majority of problems.

If you find yourself reaching for TCO, it usually means that you're mission a collection combinator.

I actually find myself using TCO really only when grinding leet code problems in order to achieve n, log n, or n log n complexity. In the real world, it's rarely ever needed. And if it is, you could always use a free monad instead.