TL;DR - Two sets of eyes is better than one.

One of the most important aspects of code review culture isn't really mentioned in the post: requiring at least one additional approval on a PR ensures that at least 2 people are familiar with a piece of code. This helps increase the bus factor on the project and ensures that knowledge transfer and developer velocity can be maintained.

Additionally, the dialogue that occurs during code review can serve as additional documentation into why certain choices were made. I use the blame layer all of the time to try to better understand the context of a particular piece of code. Being able to read through the review for the PR that contained a line of code is often incredibly useful for being able to gain context.