Gaining Google's trust doesn't happen overnight. It takes time. Think about building up your relationship with anyone. The longer you know that person, the more likely that trust will solidify. So, the reasoning is, that if Google just met you, it's going to have a hard time trusting you. If you want Google to trust you, you have to get other people that Google already trusts, to vouch for you. This is also known as link-building.
LinkTrust has been in operation since 2002 and claims to be “the most accurate affiliate tracking software on the market.” And, it may be difficult to argue with that statement. LinkTrust features a customizable interface that allows you to track essentially any sort of advertising online and offline – cookies, pixels, server posts, host,CPA, CPC, Pay-per-call, mobile traffic. You’ll also have access to “a slew of heavy-duty reports,” filter options for traffic, top-notch support and the patented LinkTrust Remote Traffic Agent (RTA).