I don't see much positive benefit coming from providers reviewing hobbyists. I am *assuming* that the review would be visible to the the gentleman in question. If so, then chances are the only reviews that would be written would be glowing ones.
Kind of the same logic why the ROS here is not visible to providers. Egos in general do not handle criticism well, gender notwithstanding. So an honest but very unflattering review written by a provider is not only likely to cause the guy to get butt hurt, there is also a pretty good chance that it would also have the added benefit of harming the provider's reputation.
Additionally, reviews could create an awkward situation for the provider. He thought he was the world's best lover, she thought he was a horse's ass. He asks her to write a review, so what does she say? Does she tell him no? If she does he will want to know why. Does she just lie? If so, she is doing her fellow providers a disservice, and blowing smoke up his ass when perhaps he needs to be set straight on a few things LOL
So, the likely result would be alot of puff pieces. Sites like P411 and Datecheck already serve as very useful verification sites. Additionally, there is the reference system. These are the provider equivalent to the guy's reviews.
Not only that, but the sort of information women are interested in exchanging about clients via references is significantly different from the sort of information men typically share in a review. We want to know if he is LE, if he is safe, any hygiene issues, was he on time, did he overstay his welcome, was he a gentleman. Physical description, skills, that sort of thing really isn't important in a reference, and if a guy is looking to get reviewed, these are probably the things he would be wondering about LOL
Last but not least, its just not discreet.