Retired state police here. Yeah, it happens a lot more frequently than what you see. Here's your problem if you are. You have to get your combination legal. A traffic citation is not a permit to continue. That usually means dropping your rear pull. What happens to your rear pull? Either you find someway to move it off the roadway or the officer will. You'll be the one responsible for any tow and storage bills, along with the citation fee. Is that a way anyone wants to spend their vacation?
Why people say they've never seen it happen is sure no way to determine if it happens. Have you ever seen a bank robber pulled over? Even those people you have seen pulled over it's most likely you have no idea why? Or if they were even pulled over and what you're seeing is a motorist assist. Even if you did see a LEO behind a double tow how do you know what is going on? You don't. There's a whole lot of traffic stops being made all over the US that you'll never see nor hear about nor will you know why.