While Amazon certainly has a vested interest in getting people to trust the reviews (they care more about people coming back to Amazon again and again than selling any one product), I wonder if they also have a vested interest in keeping a large number of products from multiple vendors available.
If Amazon ranked it's items the "proper" way, such that all one-rating products were far from the top, I imagine it would see a lot more clustering of purchases on the most popular version of every product type. All those variations that were not as popular would receive many fewer purchases, and some of those vendors might simply fold.
Amazon may have decided that having a larger ecosystem of vendors is worth more than implementing a better rating system. This, presumably, is not in the customer's interest (unless perhaps the "discoverability" of unknown products is on balance worth the risk).
Whatever the reason, Amazon certainly knows about other ranking systems, so it has to have made this choice deliberately.
For Amazon (and equally large companies) I usually tempted to put the proverb "don't attribute to malice which is adequately explained by stupidity" on its head. There's definitely a financial reason behind this.
If Amazon ranked it's items the "proper" way, such that all one-rating products were far from the top, I imagine it would see a lot more clustering of purchases on the most popular version of every product type. All those variations that were not as popular would receive many fewer purchases, and some of those vendors might simply fold.
Amazon may have decided that having a larger ecosystem of vendors is worth more than implementing a better rating system. This, presumably, is not in the customer's interest (unless perhaps the "discoverability" of unknown products is on balance worth the risk).
Whatever the reason, Amazon certainly knows about other ranking systems, so it has to have made this choice deliberately.