This discussion is always amusing, and generally always follows the same basic pattern, like this:
One poster says: It is required by law in most states! Use one or break the law and risk paying the consequences!
Another one (usually mowermech) says: No, it is NOT required by law in most states, here are the specific laws stating, proving such....blah blah blah...
previous poster replies: Wellll, I don't care what the law says, I'm not going to chance it, I chose to use a supplemental brake for safety regardless!
Response: That's fine, that's your choice. But, quit throwing out false statements saying the law requires such just to justify your choice, because truth is, the law does NOT require it in most states, you just chose to use one.
...And, there is usually at least one that tries propagating that complete myth, about insurance refusing coverage if an accident happens when not using such a system.
Does provide for some entertaining reading, if nothing else. :)