Showing "commitment to the club" can change within months, something that have been seen lately (VVD, Coutinho, and maybe even Rose). What´s the point with a long contract if you are not sure what you think about it half way through it? You know that club has all the aces if you want to leave, regardless how much you "cry".
"It's often not actually really a 5 year commitment." It is, unless both parties agree that is isn't. Again, we have seen lately players having problem to accecpt what they actually have committed themself to. If the club dosen't want to sell, the player will remain. End of.
"Not reaching a deal at that point mean it's the time to sell (see Carrick, Berbarov)." Yes, if someone whats to buy (at the right price) and if the players wants to leave (to that buyer and maybe taking a cut). A contract is a comittment ifor both parties and a player have the right to reamin the whole lenght of it, regardless what the clubs think about it. (Like Ade)
The only winner in the world of long term contracts are the agents. Neither the club nor the player can predict their respective situation in 5 years.