New York Giants + free agency?

Why do you guys think that the Giants never really try to pursue any of the areas that they need in free agency? We got Antrel Rolle, which is good, but we could definitely use a good linebacker, another good defensive end, and/or a good, reliable wide receiver. So, how come the giants never go after anyone in free agency? I would've liked to have seen maybe Julius Peppers, or Anquan Boldin go to the Giants. I'd actually really like to see either Karlos Dansby, Derrick Burgess, Elvis Dumervil, Scott Fujita, Joey Porter, Barrett Ruud, or Jeremiah Trotter head the Giants' way. I just think that every year they need some good, solid players at multiple different positions and they try to fill those vacancies by developing back-up players and developing rookies from the draft. I think for once they should try to fill at least 2 or 3 positions with experienced, good, reliable players from the Free Agency market. They already got Rolle, so maybe they should try to pursue one of the LB's I listed earlier because they already have a decent receiver core and decent defensive ends so the secondary and linebackers are where they really need to improve. My ideal pick up at linebacker for the Giants would be either: Dansby, Dumervil, or Trotter. Each one can make plays, jump start the defense they're on, and make good hard tackles. And that's one thing the Giants lacked last year was their tackling ability.