NFPA 70, commonly known as the National Electrical Code (NEC) is the number one selling standard produced by the National Fire Protection Association (NFPA). It’s the basis for the electrical journeyman’s license exam and the master electrician’s license exam.
Contrary to a common misperception (especially outside the electrical world), it doesn’t provide guidance on what an electrical installation should be. It provides the bare minimums for what an electrical installation must be. This isn’t a fine point of distinction.
There are often compelling reasons to exceed NEC requirements. There’s almost never a good reason to fall below them. Sometimes there is such a reason (usually based on practicality). The Authority Having Jurisdiction can make an exception, based on sound engineering and finding some other way to satisfy the intent of the NEC rule.