I had the exact same problem. I never understood the age limit either.
I would just have your mother call, tell them that you are 16 and book it and then just show up. If they ask for an ID just tell them that you don't have your license yet. From what I understand, they never ask for an ID. Anyone else know this to be the case?
In reality, Disney is more strict on restricting the age on the phone when you make a reservation, then when you check-in on the day of your tour.
If you ask if you can take a younger child on a tour that has a high age limit, the people on the phone will tell you outright no. Sometimes, they'll even say that if you do bring the child on the day of the tour, they won't let them go on the tour, nor will they give you a reason.
But if you lie to the operator, and then show up on the day of the tour, the cast members will hardly give you a second look.
They might be a little adamant about I.D., however. Just bring a school I.D., or your parents can bring a copy of your birth certificate, and fudge the date. They won't care.
I think there are a couple reasons for raising the age restriction.
One thing is that the tours might ruin the magic of Disney.
Another thing is that younger kids might run off and get into restricted backstage area and get away from the tour. (I bet they have had some problems in the past.)
Also, the tours are usually 3 or 4 hours long. The Backstage Magic tour, especially, is somewhere around 7 hours.
A lot of kids might not be able to pay attention for that long, and get easily bored, especially if they are not constantly seeing the characters or going on rides. Some kids might not even care about the tour at that age unless they are hardcore Disney fans (especially if their parents are the real ones who wanted to do the tour. :lol
The age limit does stink though. I can't believe backstage tours have 16 year old age limit, but SCUBA diving tours in the Living Seas only have a limit of 8 years old, which in reality can be somewhat dangerous. :shrug: