Ballet takes dedication and is much more complicated than spinning around in a circle. Just imagine holding your leg up at a 180 degree angle with all of your body weight balancing on one of your toes, whilst trying to make the move look graceful and elegant - it takes a lot of hard work and is much harder than it seems. I think it is because professional ballerinas make dances look so effortless and beautiful but in reality there are probably a million things running through their mind at one time to make it look perfect not to mention the pain of standing on your toes.
Ballet pushes all of the boundaries of the human body into some unnatural positions that are sometimes quite uncomfortable but it all seems worth it because, in my opinion, there is nothing more beautiful.