My take (feel free to flag or delete) is that the age limit is a function of liability and contract law (and therefore lawyer induced trauma) so that there can be legal remedies such as cost recovery applied to the license holder in civil court. Under a certain age range, the courts in the US have difficulty assigning strict liability to an individual as they are deemed "not competent" (like some adults no matter their physical age - myself included). For you to engage in a commercial agreement to provide a service, and take on the responsibility of that contract, and be financially responsible for the outcome of your actions is the basis for this decision. Part 107 is all about COMMERCIAL flight activity, so that is why I am theorizing this as the reason.
Take your time Jay, and by the time your ready to take the exam get a perfect score...stay safe, have fun and continue to push the envelope (safely). The world needs more driven people that are willing to excel and ask questions like why. Try finding a 107 pilot near you that is willing to mentor you and learn while you wait for that calendar date and use the time wisely....