Code reviews are so unbelievably important for a team, I can’t believe how many teams don’t do them. And it isn’t just the development team, its any team that writes code. Dev, QA, Database, Ops, everyone! If your customer service team is writing macros in Excel, they should be code reviewed!
Let me just start by acknowledging that even a thorough code review won’t catch every issue. Code reviews are pretty good at catching certain types of issues. Silly errors like using an assignment operator instead of an equality operator, or a strict comparator instead of non-strict. These are mistakes that are easy to make, and can often have very subtle consequences that are hard for your tests to catch. Fortunately, they also tend to be the types of errors that stand out to code reviewers (probably because they are simple and everyone’s looking to score points on the review).