I don’t think it’s as simple as you make it. Look at Alves would you rather have forced him to stay or voided his contract. If a player is going to be miserable it will show in their play and then you will be paying wages for a cancer in your locker room and on the pitch and the damage will be greater than just letting them gtfo
Okay Mr. Andrea Cristiano (??) if that's the case, how come it doesn't work the other way around too? How come if you have a player with 3-years left on his contract, but he's absolute shit and on high wages that no other club is retarded enough to match, how come we can't just tell that player: "Hey buddy, we don't think it's working out anymore. Can we just conveniently rescind this legally binding contract we have that says we have to pay you bucket loads of money for three more years so we can get your cancerous vibes out of our locker room?"
You know how that conversation ends after he responds to our request? "Aw, really? But Mr. Andrea Cristiano said- what? You don't care what he said? He can shove his opinion where? Well that's not very nice

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No one holds a gun to these players' heads when they sign these contracts you know. They are signed by adult men making a decision after what should be careful deliberation about committing a certain number of years of their lives to this club. You make it sound like we would be the first club in the history of football to tell a player "No, we don't want to sell you, you're still contracted to play here." He might sulk for a bit but he'll get over it.