Decentralized trust is a way to "open source" a customer/merchant database. If centralized trust is required the company controlling it can charge people to use it, for example think of listing fees as ebay charging people for access to their seller ratings. Or uber charging people to access its driver ratings.

With decentralized trust we could create a decentralized uber, where drivers get 99% of the money and 1% going to developers and providers of decentralized insurance.

One alternative to decentralized trust would be setting up a nonprofit to control the trust database, but then you are relying on the government to enforce that the nonprofit doesn't gouge the customers, manipulate the ratings, or embezzle the funds. You are basically just pushing the trust onto courts and law enforcement.