Many people look at # of reviews and average review as "social proof" about the quality of a product. The reason we do this is because it can be a useful short-cut to performing an intellectually rigorous evaluation. If Amazon removes a bunch of reviews they're removing incentives that users use to buy products.
Most retailers find that conversion increases alongside review count, with diminishing returns above something like 50 reviews. It's important enough that most of the largest retailers either incentivize reviews with rewards or run "seeding" programs where they send out products in exchange for reviews.
It's not in the interests of Amazon to be on a crusade against fake reviews. Mass fake reviews are the driving force of revenues.
AMZN will always maintain the balance between public outcry and absolute minimal effort to show that they're doing something against spammers.
From my side I maintain the right to buy the product and then write "not as described" as a reason for free return for full refund with free pickup.
Quite often vendor/seller will give you refund without requiring you to return merchandise.
I don't feel like I been abused too much by fake reviews as long as I can "abuse back" with my free return.