Plus, it would mean people would stop just incrementing a number at the end if it revealed their pattern.
"Verifiers SHOULD NOT impose other composition rules (e.g., requiring mixtures of different character types or prohibiting consecutively repeated characters) for memorized secrets. Verifiers SHOULD NOT require memorized secrets to be changed arbitrarily (e.g., periodically). However, verifiers SHALL force a change if there is evidence of compromise of the authenticator."
- NIST SP-800-63B Digital Identity Guidelines - Authentication and Lifecycle Management
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A large part of me wishes they made this a SHALL NOT. It would have caused chaos with other standards, but it would have been the right thing to do.