How come the San Francisco Giants don't want to signed any power hitters to improve their lineup?

I am big SF Giants fan, but is just dont get it why the team is not making any additions to their lineup for next season. They didnt make and offter to the the best two power hitters free agents in the market M. Ramirez and Teixeira, i just dont get it how they want to win with the same line up from last year and renteria in my opinion was not a big signing.