While Product Owners benefit from CI & CD in many ways, two key ways are consistent quality and speed to market.
First, with continuous integration the products they are responsible for are much more consistent in their quality.
Second, with continuous delivery and deployment, the products get into the hands of the users as quickly as possible showing value to users and providing users constant proof of the value of the product.
Tekton comes into the picture by supporting engineering teams with creating easy, consistent, and scalable methods for implementing CI & CD. For engineering teams, the infrastructure to support their testing and deployment components is often the most difficult aspect to set up and maintain. The infrastructure often has no clear owners or investment leading to fragility and atrophy. When an engineering team can focus on work related to their product, rather than maintaining infrastructure, their work is better.
Suffice to say, Tekton lets the engineering team focus on work related to their product while still providing a product owner the benefits of a well managed pipeline for release and deployment.