One, it gives you free VIP days, so you can properly research providers for the future. Without VIP, you can't see the ratings, rates, or juicy details of the providers. Two, it maintains her status, or gives it a new evaluation which may or may not enhance her reputation. Posting reviews also enhances your credibility with other providers, it lets them know you are a real guy and not some crazy idiot time-waster, or worse. Keep in mind, there are providers that do NOT want reviews for various reasons of their own.
Besides posting reviews, you should also post on your local regional board so your fellow mongers and other providers get a feel for your personality, and that you are an OK guy. In short, do everything you can do to make yourself look good to providers, the more favorably you impress them, the easier it will be to make dates with them
Posting is a personal choice, but I think getting your name out there in a favorable light is very important to you. I tell this to providers who ask about getting more clients and reviews as well. Bottom line, if you choose not to write reviews, it's no one's business but your own. Many think it's too much of a pain to do them, but it's TER's site, and their rules.
Swim