Older free agents typically sign after the draft in part due to the compensatory pick formula. It is in the free agents interest to go to a team that has not drafted a player at their position. The Landry and Mathieu visits are contingency planning based on who the Saints draft and what other options the players have post draft. It makes no sense for either side to sign before the draft unless the Saints were going to overpay. The fact they are both still on the market implies no team wants to meet the player's salary request thus the advantage is to the team.