They come in the data package Yahoo is using. Just deciding what can or can't be traded by retail traders is a huge job, let alone staying on top of it to filter them out. That all costs money, why spend it when the only benefit is???
I get the feeling you're inexperienced at trading highly leveraged and complex instruments. Learn more before you blow up your account. Also understand that trading options can expose you to far more than just your original account balance. Brokerage firms can and will sue you for losses, destroying your credit score forever.
