@The Engineer - wihile I don't actually know this I cant fathom that ski manufacturers respond to PSIA - they are trying to sell skis and PSIA is selling instruction training team building etc.
The % of people who take a lesson is small enough - but then the % of those who want a zipperline mogul lesson is much smaller yet.
Switching to the skinny vs wide debate here is the crux of it:
The loss is NOT symmetric. I can still have sufficient fun with a fat ski on the groom. But give me a skinny ski in 3-d powder, chunked up powder crud etc and the fun factor is essentially gone. I have rossi soul7s (100+ waist) and take em everywhere: groomers bump woods hikes etc.. I also have Rossi Scratch full mogul ski (62.5 mm waist). Great in moguls, still fun on the groom. But decidedly NOT fun in deeper snow, especially skied up broken snow.
Back to instruction:
Not sure what part of the country you are in or where you ski but you should be able to find instruction in zipperline, it just will take more work.
Mt Hood has summer mogul camps, including weeks just for Adults.
This is at Whistler: http://momentumcamps.com/m/signup/dates-rates/
Personally, i'd love to see more moguls, more mogul skis, and more (good) mogul skiers on each and every hill.
But people will ski the way they want to (and that's fine too)