We have coding standards. The developers are good about following them, and some coding standards problems can even by caught automatically by static analysis tools.

But coding standards don't prevent logic errors, or requirements misunderstandings. Even the best developers make those kinds of mistakes and we catch a significant fraction of them during code reviews.

The other major benefit of consistently doing code reviews is learning. The attendees often pick up useful new techniques. And you spread knowledge of the code base around the team, which reduces the organization's dependence on any one developer and also brings out opportunities for code reuse.