OH MY GOSH, you are my new best friend! :D
I haven't yet seen another person on Answers who rides real dressage!
I'm a fifteen year old. I have done mostly hunters, but I'm starting to do combined training and the dressage makes a huge difference. I ride at two barns: at one, the trainers are from polo and Olympic eventing, and at the other, it's a normal hunter-jumper barn (I ride there for my school's equestrian team; I wouldn't ride there normally).
I actually disagree with an above poster that said dressage is more expensive. I can't afford a horse, or even to lease a nice one with which to succeed in hunters. The horse I ride is NEVER going to have the movement for hunters. However, he's big and scopey enough for jumpers, but he's so awkward that getting him around the tight turns can be difficult. We do a ton of dressage, and it really helps. You wouldn't believe how easy it is to get that big boy collected right as he lands and wheel him around to shave seconds off our time, simply because we've had such an extensive dressage background. We're aiming to take him to a combined training show soon, and I am confident that I'll be able to place way better on my cheapie, ugly horse in CT with my used tack than I would in hunters.
I think the REAL problem for teens is that it's too much work for so little excitement! It was a good month before I got my horse really round and forward to get that beautifully balanced, forward trot. Until then, it was a LOT of frustrating, tiring lessons where we didn't seem to get very far. Most teens don't have the patience for that. :( It's a shame: I love that feeling when they're truly round, forward, and balanced (we haven't really started working on collection yet aside from 'getting it together' in jumpers :D ), and I think that's WAY better than soaring over a jump.
I know that, in my area, there simply AREN'T any good dressage trainers! I have the only good ones in my area. The others are either all high-end hunter or jumper trainers. You either do hunters or jumpers, or you don't ride. Period. There is one eventing barn, but I don't think they focus on dressage, either, although I don't know very much about them.
It really frustrates me in my school equestrian team lessons when my trainer asks me to shorten my reins on a green horse when I've just gotten him to begin to stretch down for me, which usually backfires and makes him tense and bracing instead of round... but what can you do? People just want to do front to back instead of back to front because it's quicker. It's a shame.
Where are you? I'm in Georgia, and I know that this whole region is all hunters and some western pleasure people.