I don't think the price is the reason, but I lack another explanation.
Knowledgeable kayakers guess the price of the AI to be around $4,000, and react with surprise when I tell them the price.
High end kayaks, especially after you buy the matching high end paddles and accessories, can approach or exceed the price of the AI, but they certainly can't approach the speed and fun.
My wife is still something of a beginner to kayaking, and (hoping to avoid trouble here) is not currently in shape to compete in a triathlon. Even with the best conventional kayaks on the market, people at that level don't go on a little 16 mile jaunt, like we did the other day in our AI's.
An AI will last a long time. I'm hoping for at least 20 years from mine, as I have another rotomolded kayak nearly that age. That's 7,300 days for a little over $3,000. There will be some expenses along the way, like when I drop a Mirage Drive in the creek, but not many (I hope!) Owning an Adventure Island costs less than a cup of coffee per day. It's the best boating bargain anywhere. What other boat can do all the things an AI can do, let alone do it for that little money?
Times are tough for a lot of people, but who can afford to waste another day on the planet without owning an Adventure Island?
(Just practicing for tomorrow...