Most people are inherently familiar with the concept of a "container", in the sense of something that holds other things, regardless of whether it's a physical container or a data structure.
"Iterator" might not be as clear as "container", but at least most people are familiar with the concept of doing something repeatedly, whether it's some physical action or executing some chunk of source code.
"Monoid" just isn't like that. It may be concrete when constrained to the context of mathematics or programming, but it's quite meaningless outside of those very specific contexts.
But that isn't really true. Addition and multiplication are both real-world examples of monoids that everyone is familiar with (obviously, these aren't physical things, but I don't see why that's relevant).