Thing is, companies aren't just a web of contracted individuals.
Companies gain efficiencies from reduced transaction costs; this is the basic theory of the firm, the reason we have firms at all.
One of the big ways transaction costs are reduced is by increased trust, trust at the human level. Interactions don't need lots of checks and guards and ass-covering because there's mutual trust, at a human level, that people are working together on a profit-making enterprise.
Breaking trust affects efficiency. If someone threatens to leave, you can't make future plans that assume they're in place. People aren't cogs that can be trivially replaced; on-the-job knowledge makes people more productive and takes time to acquire. So if someone's future presence is uncertain, timelines stretch, more people need to be allocated to it to account for risk of people leaving, and so on.
And this affects other trust relationships further out. A manager of a team or a product area may not be able to deliver on commitments that serve a strategic purpose of the company directed at a higher level.
It's not "purely business". Businesses run on trust; companies are collections of individuals with a higher degree of mutual trust, and the more trust they have, the more they can eliminate inefficiencies caused by lacking trust. That's why companies work at all.