Wrong. This forum has 2.7 million registered accounts, and the number of active users is counted only in thousands. Amazon has 300 million users. The demand for buying goods with BTC is tiny, even if you assume that every visitor of this forum wants to buy things with Bitcoin, which is not the case, since many people want to hodl or wouldn't trust sellers with Bitcoin transactions.

There's not enough interest neither from sellers, nor from buyers. I've seen this happening with Bitcoin freelance sites - extremely low volumes when compared to mainstream sites with no signs of growth at all.