[CryptoPunk]

>>"Forcing" a trusted party into the exchange is the optimization, and it only works because everyone does it.

The point you're skipping over is that there are network effects in the role of trusted third party, leading to monopolies/oligopolies, which can extract artificially high fees.

This is where distributed consensus has an advantage: it can provide the same and even stronger guarantees on the integrity of records, while preventing any third party from using their monopolistic position to extract high fees.