That's not true, there are many "open loop" control systems, which do not use feedback.

Well, that is perhaps a matter of terminology. I wouldn't call those (including everything mentioned in the Wikipedia article) control systems at all, and every textbook I've ever seen on control systems is exclusively about closed-loop systems. "Open-loop control" is practically a contradiction in terms.

I suspect that open loop control is less common in natural systems than generally believed

It should be the default assumption in the life sciences, that (closed loop) control systems are present everywhere you look.