The primary motivation behind any code review is to improve the overall quality of the code. Code quality is very important. This almost goes without saying, especially if your code is part of a team project or is accessible to others, such as open source developers and customers through escrow agreements.
If every developer was free to code as they pleased, you would end up with the same kind of code written in so many different ways, and ultimately the code would become an unwieldy mess. That is why it is important to have a coding standards policy that outlines the company's coding practices and code review procedures that are to be followed.
When code reviews are carried out, colleagues will review the code of other colleagues. Colleagues will understand that it is only human to make mistakes. They will check the code for mistakes, coding that breaks the company...