You have probably seen the polls that show that very few people attend a congregation because of the pastor. The majority attend a congregation for the first time because a member invited them. The same works with an invitation to generosity. Most folks will never learn to be generous without an invitation to generosity.
Think about the daily bombardment of ads encouraging us to buy a product. It is no wonder that we are overwhelmed in our homes with stuff. We cannot escape the consumer driven lifestyle of America. Then we send out one letter a year about generosity and wonder why our members fail to give.
Churches and ministries need to communicate their mission and the need for resources to support the mission. Churches and ministries also need to clearly articulate that generosity/stewardship is included in discipleship. Growth as a believer includes growth in generosity. So many believers are so close to the joy of salvation, but they are choked out by the cares of the world and greed.