The thing with imperative programming is that you don't really need to know the language to at least get an idea of what's happening.
Lisp is so dense that while you can pack an unbelievable amount of programming into a small chunk, approaching it as a beginner is daunting. There isn't a really good way to 'build' on an algorithm and learning it is significantly harder than learning C# or Java or even better yet, Python.
It's like saying, 'Linux is easy to learn! You can do so much in so few characters! It's so powerful! And look, robust manual pages for all!'
Yeah, that's true, but handing a user some pipes and greps isn't going to explain what the hell they actually do or better yet, how to leverage that into something useful. It's just going to look like greek to anyone who sees it and a huge effort has to be made to get to the point where you can even begin to understand what's happening.
Imperative programming doesn't ask you of much. 'Here is a class. Here is the main method. Write some stuff in here. Here are some basic methods in the default libraries and their expected inputs. It's going to execute line by line. Go nuts.'
And that's really the difference here. Lisp asks a lot of the user up front. Python doesn't. C# doesn't. Fuck, Python is so loose that you don't even really need to know what any of the structure is to start writing something that kicks back some output. Yeah, as a group that understands Lisp and Scheme and Haskell and F#, it's really easy to say, 'Lisp isn't THAT hard', but that's bullshit. Lisp IS that hard. Lisp is a very difficult language to pickup when you are starting at square one and it's only marginally easier if your background is purely imperative languages. Misrepresenting that is a bold-faced lie.