The Franchise Tag

In pro football, there is a title which no player desires to have. The dreaded franchise tag. Once a players contract is up, contract re-negotiations begin. Sometimes, if the player wishes to leave his team but the team wants to keep him, they place the franchise tag on the player. This tag signs the player to a one year contract, but other teams have the option of matching the contract and signing the player, but giving up draft picks to the other team in exchange(http://www.nfl.com/news/story/6194643). So my question is, why would teams want to keep a player on their team who has no desire to play for them? With team morale being so important, and players whining about everything, forcing a player to stay on your team while he is unhappy seems to be an incorrect philosophy.