Okay I'll explain this to you. As people age, they do quit sport. Not because they physiologically have to, but socially they are somewhat expected to. After highschool, you are expected to get a job and give up on the fun and games. So yes, you do have a point in some what.At least that has been the mentality for the older generations, but that is changing. Just like many adults have continued playing video games, people aren't going to quit something fun like skiing park because its 'only for young people....'
But if you look at park, which realistically started in 2001 for many mountains was for the most part done by younger skiers 14-21, because from a motor learning and brain development perspective those are the ideal age and the most likely age to part-take in high skill and high risk activities. In 2001, there was little knowledge or coaching done within the sport.
Now, we have a much more structured approach to the sport. Nearly every hill offers park lessons, allowing older people to safely enter the sport and not feel like an ass with the kids. And those 14-21 year olds who were involved with the sport are still staying involved, many may quit, but not all.
Besides the point that popular culture in general is fixed on the youth, the reason why the sport appears to be young is because the athletes in the videos, competitions and magaizines are young. They were able to benefit from the skills discovered from the older athletes and apply them at a much younger age, with coaching and better/ safe facilities (just compare super park to the JOSS, what do you think was more dangerous?).
Concepts from other sports are now being applied to park skiing, it is no longer an 'extreme sport' as now have a better understanding of the sport. That being said, the sport will go through a plateau, as progression is decreased with the limitations of training techniques (much like gymnastics has done). In 10 years, the average competitive skier will be older, because it will not be about learning a skill, but maximum power output (which favors a 28 year old over an 18 year old). Look at snowboarding, the average age is the x-games is much higher than that of skiing because it is now reaching that point.
Because we understand the science of sport better, older athletes are able to stay involved longer because they understand the basics in technique, not to mention physio therapist now also provide services to stay active in sport that used to only be available to keep working.
From a demographic perspective, it will also get older. Gen Y (in Canada at least) is a much larger cohort than that of the kids these days, elementary school are closing down, while right now getting a job or entering university is extremely competitive. So if you analyze it based on statistics alone, it will get older. Furthermore, the average kid is much more unfit compared to Gen Y, so who has the greatest likelyhood of higher sport participation?
Obviously each generation is better then the one before in performance because knowledge is passed down, but the number will be different. The youth will always have most influence on the progression of the sport but that doesn't mean there isn't a spot got the old guys to have fun.
Go eat your veggies, and stay off my jump son.
-Fools rush in where angels fear to tread.