Vulcans have been assisting humans since before the formation of United Federation of Planets. After the first contact and before the first deep space mission of mankind, they did seriously assist mankind in the development of warp drive and several other things (Archer's father told this to Archer in the very beginning of Star Trek: Enterprise TV series).
But, in the Star Trek: Enterprise TV series, we also learned that Vulcans were holding back information from humans. They also didn't like it when humans start their deep space missions. They also killed Admiral Forest on Vulcan.
It was Archer's efforts and a Romulan conspiracy which really united Humans and Vulcans. But, before that, why did Vulcans assist humans at all for a century? They even appointed an Earth ambassador here. Why? What were the benefits from an inferior race? Definitely, there are always mutual benefits in such cases and Vulcans were bad guys too (not to forget logical too).