Because there are a lot of people who only think they know. Suspensions are complex things, and just because a product is advertised or just sold doesn't make it a good product.

I've learned a great deal, and have plenty left to learn, about springs, spring rates, dampers, damping rates and what does/doesn't work in the past several years. The biggest thing that I learned was that I had little clue as to what makes a good suspension setup and what doesn't. Having the money to buy Teins doesn't mean that person knows squat about suspensions.

Here's something to chew on, if Teins were so great, then why do the top running STS (that's an autocross class) and ITA (raod racing...SCCA specifically) cars all run Konis?