Why? Would you let your employer tie you to the company that way? Where you can't leave if you get offered more money or a raise elsewhere? Where you can't walk out if you're being bullied or overworked? Why the hell are footballers expected to be slaves to their jobs?
I know that footballers seem to get a raw deal, as far as contractual conditions, but they did sign the contract and it is both their responsibility, and that of their agent's, to read the contract before signing it.
In the UK, if you are an employee, you cannot just walk out of your job - you have to give notice, (the length of notice you have to give is in your contract) and if you don't, you can be disqualified from claiming benefits for up to six months. If you walk out without giving notice, to go to another job, it can affect you, for reference purposes. Employers talk to each other, and if you behave like this, you will get a reputation, that will put employers off you. Most new employers allow you to work your notice to your old employer before joining.
Footballer's sign these contracts and they have a responsibility to keep to them. If they don't, then they have to pay the price. As for being bullied, I don't think there is much of that. Footballers have big egos and the vast majority of them are not prone to bullying. They are confident and are able to take "knocks". They have to be to play football.
However, I agree that their conditions should be clearer and fair. I would not like to attempt such a task as it would have to be done on an international scale, as well as European and on an individual country basis.
I am glad that the agent is being investigated by FIFA. Players rely on agents so heavily, that they can end up in a legal mess due to their agent's mismanagement of their affairs.