This is the big one IMHO. I've been part of teams where there was zero code review, and where the code reviews were intense, and for sure people write much better code (generally speaking) when they know it will be reviewed. We all do it, even if subconsciously.

I do advocate a balance though. Ridiculous code reviews tend to slow the process down immensely, which is good for some things but bad for others. Finding a good balance is super important IMHO