or are biased because they are getting it for free (seriously like 95% of these "unbiased reviews are 5 stars)

You took half the sentence there, I didn't mention that as the only reason :)

I am saying here that the absolute majority give 5 stars and it is very rare to find one of these reviewers coming back after several months to update their reviews because the reviewers didn't pay for it in the first place.

Unlike the reviewers who got it for free, reviewers who paid for it are not forced to write a review. This is essential because when you are not forced to write a review, you only write when you have something positive/negative to say about the product. This explains why the majority of these reviews are very simple and talk about the aesthetics: they couldn't find anything else to say after using the product for 2-3 days. While in the case where the customer paid for the product, they will come back after few months to complain/give credit to the product.

One last point, I am not posting this to offend anyone in any way, I know that there are many people out there who do the right thing, but these people are sadly getting massively outnumbered and the thing is getting out of hand. Seriously shopping on amazon is starting to become really painful because of this and I hope that amazon does something about it