It is common practice in contact law that those persons who create something new and sensational, in say the world of IT, that created idea from within the bosom of the company, belongs lock stock and barrel to the company.
Sport is very similar. While ever an athlete is in the employ of a particular Sport organisation, that athlete is expected to give not 100% but 110% to achieve the ultimate goals of that organisation, and thereby implies, the owner's.
There are significant advantages to the athlete in such situations.
Tenure
An athlete has tenure and security for the period of the contract. This can never be underestimated and is of great value, especially considering that a host of similar athletes are vying for such tenure.
Injury
An athlete's contract will inevitably safeguard their financial welfare in case of injury and injury for an athlete is serious business, very serious indeed. This is a huge incentive to secure a contract.
Family welfare
A married athlete with children have a lot more to consider than just Sport. A family requires income security, schooling of choice for the children, a social arena for the spouse, a family soft spot for the athlete.
Time to move on
There are occasions when it is time to move on. An athlete may have grown beyond that Sport organisation, there may be family health issues with wider family considerations, perhaps retirement becomes an option, but whatever, a good contract will allow such issues to be dealt with sensitively and in good standing.
Yes, athletes are bought and sold, that is Sport. It's designed to be win-win for everyone involved. Sadly, there are occasions when it doesn't work out. That's the reality as well.
A Minister of a Church is in a similar position. The charge the Minister has is two fold though. One is an inner Calling to the Ministry of the Gospel of Jesus Christ. The other is like a contract whereby the Minister serves that congregation or Mission agency and the agreed parameters are spelt out. That's the ideal.