This sounds like a coordination problem [1]. If only one person writes a letter to their representative, it doesn't do anything and that person is the only one who comes out at a loss of x hours of their time. No policies are changed and everyone is stuck in a bad situation.
If a significant portion of the representative's constituency sends letters and the net political effect overcomes the amount of donations the representative gets from intelligence companies, maybe they will actually begin an initiative for policy change. Everyone is better off, but it's hard to convince a critical mass of people that think it will succeed.
[1] http://raikoth.net/libertarian.html#coordination_problems