This is an exciting question for me to answer. I write bios for BMX riders; in fact, I'm interviewing a champion BMXer this afternoon. To answer the question, BMX is one of those sports where the major skill required is proper execution. A BMX contest is not as subject to the judge's personal opinion of the rider. Fairly enough, winning depends on who executes a stunt the best, with best being relative to the stunt. For example, whoever completes the course the fastest, whoever jumps the highest, and so on. A BMXer can be young or old. A BMXer doesn't have to be the cutest, the smartest, or the most popular person in the world to be a winner. They just need to have the best execution of the stunt.
Attitude is another reason why BMX is such a popular sport. Most of the people involved with the BMX sport industry have positive and encouraging attitudes. They want kids to have fun first, because success will follow with practice and time dedicated to becoming better. But, having fun is the critical attitude threaded throughout the industry.
Finally, the type of bike doesn't matter. The proper size does matter. While there are standard sizes for the industry, as much as possible, the bike should be fitted to the rider.