For the same reason why it is important to know who owns the house you are are living in or the company for who you work. Or the company who runs a factory across town.
It is a question of accountability and also stability.
When you start a business on a domain and you rely on that domain it is important to know that this domain is well maintained. What if the company is giving your domain to someone else. And you can't do anything about it because the company is gone.
Top level domains are a key to the infrastructure of the internet, there should be transparency and accountability. Otherwise this market will fail.
