There are a lot of reasons a guy may not choose to review a particular provider. It may not even have to do with a provider sometimes.
Some don't review until they need premium access.
Some don't because the provider they saw has multiple reviews already on the first page.
Some because they heard a provider they like won't see them if they've seen a certain provider.
Maybe they had such a great time they can't put it into words (yes it does happen).
The list goes on and on. It's not always a racial reason.