Ski ballet was a mandatory event in freestyle in the early 90's. Coaches would talk about it back in the day, but everyone never really liked the discipline. Ballet finally died the day ski resorts started pushing up jumps with their CATs.
Ballet made sense in the 70's and 80's when the concept was still based off hot dogging. It was getting down the bumpiest hill and putting on the best show. Ballet was like removing the hill and the bumps to focus on style and how well they perform surface tricks. But as freestyle moved away from hot dogging and focusing on technical aspects such as turns and jumps. By the 90's, the modern course was standardized and jumping was now the craze. Ballet lacked the speed and show that moguls and aerials provided. It was too elegant for modern freestyle.
The final nail for ballet was the gear. With long skis, one ski did everything. Deep powder, GS turns and bumps. Shorter skis and longer poles were a necessity to do this stuff. Most athletes never bought the gear and no development in the sport happened by the lack of popularity.
Ballet skiing isn't dead. Most of our lip tricks, surface tricks and everything we do that does not include a rail or a jump, is a progression of ballet. Sure the gear is different and the location isnt the same, but I would argue that the ideology remains the same; you can still do tricks without a jump and still have fun and look good at the same time. Urban today is almost a take on ballet and park.